The invention relates to the technical field of rail vehicle manufacturing, and particularly discloses a fast bogie side beam installing and welding device. The fast bogie side beam installing and welding device comprises a supporting platform, a longitudinal positioning mechanism, a transverse ejecting mechanism, a transverse limiting block, vertical ejecting mechanisms, reverse deformation ejecting mechanisms and a plurality of magnetic force limiting blocks. The longitudinal positioning mechanism comprises a sliding plate and a driving mechanism, the sliding plate is provided with a positioning groove, the positioning groove is used for supporting and positioning a positioning bogie side beam, the driving mechanism is arranged on the supporting platform, located below the sliding plate and used for driving the sliding plate. The transverse ejecting mechanism is arranged at one end of the supporting platform. The transverse limiting block is arranged at the other end of the supporting plate and corresponds to the transverse ejecting mechanism in position. The vertical ejecting mechanisms are arranged on the supporting platform. The reverse deformation ejecting mechanisms are arranged on the supporting platform. The magnetic force limiting blocks correspond to rib plates of the bogie side beam in position in a one-to-one mode. The problems such as assembling deformation caused by insufficient manual pressure can be effectively solved in the bogie side beam welding process.