It was compiled by campaigners, who say the missing girl's parents - and even her siblings - have been threatened with violence.
Most of the abuse is posted on social media and claims Madeleine's parents, devout Catholics Kate and Gerry McCann, were responsible for her disappearance.
There is no evidence to suggest this is true, but the abuse continues to be posted.
Comments have been made suggesting that the couple should be tortured and "burn in hell".
Scotland Yard says it is investigating.
In a letter to campaigners, the Met said: "In consultation with the Crown Prosecution Service and the McCann family the material will now be assessed and decisions made as to what further action if any should be undertaken."
Online child protection expert Jim Gamble said: "Everyone is entitled to an opinion but when it becomes grossly offensive, when it becomes menacing, when it's causing anxiety and distress, when it's done for that purpose then there must be a criminal justice intervention."