Here is the best explantion ive seen so far about the whore of babylon in revelation :
FIFTEEN EVIDENCES that the ROMAN CATHOLIC CHURCH is MYSTERY BABYLON the GREAT, THE WHORE OF REVELATION 17.
Who is the whore/woman in Revelation 17? God has given us similarities to prove conclusively that she is the Roman Catholic church. What are these similarities of the whore with the church of Rome?
1. The WOMAN which thou sawest is that great CITY, which reigns over the kings of the earth. Revelation 17:18.
Question: Which city reigned over the kings of the earth in the first century?
Answer: Rome, no doubt. The Roman emperors were called "Pontifix Maximus". So too are the popes called by the same title.
2. She is called the "GREAT WHORE" 17:1. A whore is unfaithful to one husband, by having relationships with many suitors. So is the Roman Catholic church, unfaithful to God's Word as seen by her adopting so much false, unbiblical doctrine.
3. "With whom the KINGS OF THE EARTH have committed fornication. 17:2. The Roman Church has always sought to further her purposes by controlling politicians, kings and governments. She is the state church in so many countries like Spain, Portugal, Italy, Poland, South America and Ireland. She seeks to control governments in every country. In Revelation 17:3, she is sitting on a beast, as a rider sits on a horse controlling it.
The early Church kept separate from the State because its task was to win people to Christ, baptise and teach God's Word. The Roman Catholic Church's association with governments is outside God's instructions, hence God calls this relationship "fornication" with the kings of the earth.
4. "Inhabitants of the earth have been made drunk with the wine of her fornication." 17:2. It is very hard to reason with a drunk person. The alcohol controls his mind so that he cannot see reason. So it is with many Catholics world wide, who are so convinced of the false doctrine of the Roman Catholic church, even though the Bible so clearly oppose it. They cannot see the truth of God's Word and salvation. They will not search the Scriptures to see if the Bible's claims are true. Acts 17:11. They are controlled by false doctrine, like alcohol controls a drunkard, so they cannot see Bible truth.
5. She sits on MANY WATERS 17:1. 17:15 tells us that "The WATERS which thou sawest, where the whore sitteth, are peoples and multitudes, and nations and tongues." The Roman Catholic church has an influence in many, if not every nation in the world.
6. She is FULL OF NAMES OF BLASPHEMY. 17:3. Rome claims titles and attributes which belong only to God, such as 1"Holy Father", 2"Father", 3"Monsignor" = my Lord, 4"Mother of God", 5"Pontifix Maximus", 6"Pope" = Father of Christians, 7"Reverend", 8"His Holiness", 9"Filii Vicarii Dei" = in the place of the Son of God.
7. "The seven heads are seven mountains on which the woman sitteth." 17:9. Rome is well known as being built on seven hills.
8. The woman was arrayed in purple and scarlet colour. 17:4. Popes, cardinals and priests dress in scarlet on festival occasions.
9. Decked with gold and precious stones. 17:4. Much gold and wealth is possessed by the Roman church.
10. Having a golden cup in her hand full of abominations and filthiness of her fornication. 17:4. Much sexual immorality is committed by priests such as fornication, homosexuality, child molestation etc. This is hateful to God.
11. "Mystery". 17:5. Much mystery exists in her services. For example, Latin services, converting bread to body of Christ, how long must people spend in purgatory etc.
12. Babylon the Great. 17:5. Roman Catholic mother and child worship was adopted from the ancient mystery religion of Babylon's mother and child worship. As Rome conquered counties, it adopted their religions.
13. The Mother of Harlots 17:5. Rome has given rise to many other religions, with practices similar to herself.
14. The woman drunken with the blood of the saints, and with the blood of the martyrs of Jesus. 17:6. The Roman church has constantly persecuted, tortured, and burned at the stake, any people who disagree with papal control and who try to break away. For example, John Huss, Savonarolla, etc.
15. The ten horn nations that the Roman church tries to control, turn on Rome, hate her, strip her wealth, EAT HER FLESH, and burn her with fire. 17:16. Eating her flesh is a very clever judgment on a system that claims to eat Christ's flesh every day. As Roman Catholicism eats Christ's flesh, so too will the antichrist eat Roman Catholicism's flesh in the future seven year Tribulation.
Excerpt taken from :
http://www.users.on.net/mec/answers/64b_ro.htm