The invention provides a system for supporting and adjusting sleepers at rail traffic bridge steel beam crevices and an erection method thereof and relates to the technical field of bridge design construction. Small connected cross beams and small movable longitudinal beams are erected at steel beam ends respectively, the small movable longitudinal beams can produce limited displacements on the small connected cross beams, sleepers are erected on the steel beams and the small movable longitudinal beams, gauge adjusting devices are arranged among the sleepers in a beam crevice range, the smallmovable longitudinal beams and the gauge adjusting devices jointly and automatically adjust separation distances of the sleepers during dislocation or longitudinal deformation of the beams, and a sleeper erection system having coordinative deformation capability is achieved.