Abstract: A hydraulic loading tractor power take-off（PTO）output shaft testing device with attachable load trailer was designed to address current situation where most load trailers were only suitable for tractor traction testing, which did not fully simulate complete field operation status．This device enabled tractor PTO testing while meeting requirements of national standard for load trailer traction testing．Compared to commonly used DC power dynamometers, hydraulic dynamometer used in this device exhibited faster system response and more stable speed, resulting in better overall loading performance．Dynamic loading tests simulating torque load spectrum of tractor PTO field operation were conducted using this testing equipment．Results showed a good correlation between actual loading torque and test data from torque load spectrum, with a goodness of fit of 0.83．Through data analysis, actual response time of hydraulic loading system was calculated to be approximately 2.1 s, with a maximum overshoot of 7.52%, both within controllable ranges．By inputting torque load spectrum, this testing equipment could effectively simulate working status of tractor PTO in field operations, providing reference for subsequent comprehensive field simulation tests on tractor traction and torque loading．