The invention relates to the technical field of speed changer testing, and discloses a speed changer testing device. The speed changer testing device comprises a first locking assembly, a second locking assembly, a force application assembly and an angle gauge, wherein the first locking assembly can lock a first output end of a speed changer, the second locking assembly can lock a second output end of a speed changer assembly, the force application assembly is connected with the input end of the speed changer, and the angle gauge is used for measuring the rotation angle of the force application assembly. When the speed changer assembly is put into a gear, an operator applies force to the force application assembly, the force application assembly drives the input end of the speed changer assembly to rotate until the force application assembly reaches preset torque, the angle gauge measures the rotation angle of the input end of the speed changer assembly in the rotation process, and calculates the meshing situation of gears of a transmission system in the speed changer assembly at the gear according to the rotation angle of the input end of the speed changer assembly, a gear assembly does not need to be disassembled, operation is convenient, and the testing efficiency and accuracy are improved.