The invention discloses a hydraulic motor and speed reducer comprehensive test bed. The hydraulic motor and speed reducer comprehensive test bed comprises a main oil pump, a tested hydraulic motor, a tested speed reducer, a loading speed reducer, a loading hydraulic motor, a power recovery motor, a main oil path, a power recovery oil path and an oil supplementing path. The power recovery oil path comprises the loading hydraulic motor, a power recovery bridge-type loop and a power recovery motor. An oil outlet of the loading hydraulic motor is connected to an oil inlet of the power recovery motor through the power recovery bridge-type loop. An oil outlet of the power recovery motor is connected to an oil inlet of the loading hydraulic motor through the power recovery bridge-type loop. According to the hydraulic motor and speed reducer comprehensive test bed, loads are simulated through the loading hydraulic motor, part of power is recovered through the power recovery oil path so as to drive the main oil pump, the performance and service lives of the hydraulic motor and the speed reducer are tested, energy waste is avoided, and the advantages of energy conservation and emission reduction are achieved.