The 60-year-old from Wokingham suffered serious leg injuries when she fell from the Tilehurst Road bridge into the path of the 6.37pm train from Basingstoke as it approached Reading West station shortly after 7.10pm.
Paramedics took her to the Royal Berkshire Hospital after rescuing her from the tracks with the help of fire crews from Wokingham Road fire station.
British Transport Police (BTP) closed the line and Tilehurst Road in both directions for nearly two hours causing severe delays and tailbacks for commuters.
BTP spokesman Alexander Oliver said officers are investigating the incident but say they are not treating the incident as suspicious.
Anyone who may have see the woman on the bridge or has any information about her should call British Transport Police 0800 405040.