The invention provides an automobile gearbox shaft fast assembling table, and solves the problem of low efficiency of manual assembling of gearbox gear shaft in the prior art. The talbe also solves the problem that after the completion of assembling the gear shaft needs to be moved to the suitable position by a worker, and the labor intensity is high. The table comprises a machine frame and level support frames. A worktable is placed on the machine frame. A first slide rail is placed in the length direction at the center of the level support frame. Two electric hoists are placed slidingly on the first slide rail. A slide rail installation frame is connected vertically between two support frames. A second slide rail is placed in the length direction at both the left and right sides of the slide rail installation frame. The second slide rail is provided with a hydraulic cylinder support frame. A piston stem of the hydraulic cylinder passes vertically through the hydraulic cylinder support frame to be connected fixedly with a down-press component. Fixture support frames are placed on the level worktable located at both sides of the slide rail installation frame.