Arrests for sexual offences on the network have also increased by 36% since 2015.
The "Report it to stop it" campaign has been re-launched as police estimate 90% of people still do not report offences.
The Mayor of London encouraged Londoners "to speak up and report unwanted sexual behaviour".
New figures released by Transport for London (TfL) show annual reports of sexual offences have doubled from 1,023 to 2,087 in 2015/16 after the project began.
Siwan Hayward, TfL's Head of Transport Policing, said: "Our new 'Report it to Stop it' film builds on our previous campaign's success and encourages victims to come forward and report anything that makes them feel uncomfortable.
"No matter how insignificant they feel it may be, every report is taken extremely seriously by police and investigated so the offender can be caught and brought to justice."
Reports of sexual offences on London's transport network have doubled to over 2,000 a year in the last five years, according to new figures.