The invention discloses a robot reducer transmission performance comprehensive testing device. The robot reducer transmission performance comprehensive testing device comprises a base (14), wherein a drive motor (1), a first coupling (2), a reducer input end torque angular displacement sensor (3), a second coupling (4), a to-be-tested reducer (5), a third coupling (6), a reducer output end torque angular displacement sensor (7), a fourth coupling (8) and a brake (9) are arranged on the base (14), share the same axis on the level direction, and are connected in sequence, and the drive motor (1), the reducer input end torque angular displacement sensor (3), the to-be-tested reducer (5) and the reducer output end torque angular displacement sensor (7) are respectively arranged on the base (14) through a motor support (10), a first support (11), a to-be-tested reducer support (12) and a second support (13). The robot reducer transmission performance comprehensive testing device meets the requirements of transmission performance tests such as high precision composite roller movable teeth transmission reducer ratio, return difference and efficiency, and thus testing efficiency and testing accuracy are high.