The invention discloses a detection tool structure for a floor rear lower crossbeam, and belongs to the technical field of crossbeam detection. The detection tool structure comprises a bottom plate, avertical plate is fixedly mounted at the top of the bottom plate, a lifting block is slidably mounted on one side of the vertical plate, a lifting plate is fixedly mounted on one side of the liftingblock, two transverse plates are fixedly mounted on one side of the lifting plate, rotating shafts are rotationally installed on the opposite sides of the two transverse plates, a positioning table isfixedly installed at one end of each rotating shaft, two movable blocks are installed on the side, away from the corresponding rotating shaft, of each positioning table in a sliding mode, clamping rods are fixed to the movable blocks, clamping blocks are fixed to one ends of the clamping rods, and a vertically-arranged track plate is installed on the bottom plate in a sliding mode. According to the detection tool structure for the floor rear lower crossbeam, fixation and electric fixation of the crossbeam are realized, the positioning is stable, then the detection is facilitated, meanwhile, the adjustment on the spatial positions of a detection assembly and the crossbeam is realized, through cooperation with rotation adjustment of the crossbeam, the omnibearing detection of the crossbeamis facilitated, and great convenience is provided.