Research conclusions: The float tow and jack － in method is the innovation based on the traditional float toe method． It is different from the traditional float toe method in the power to make the girder longitudinal moving． Namely，it uses the jack － in device at the rear end of steel truss to substitute the traction device in the front of the steel truss，with the features of using simply equipments，easy operation，even velocity，smooth running and ensuring the security．