Background: Rural labor force in Korea has recently been steadily decreased of population and increasing of aging population. Therefore, small multi-purpose cultivator is widely used for field operation due to the field of small scale in Korea. Methods: This paper measured and analyzed the engine torque of the cultivator by ditching rotor operation, and then fatigue life prediction of PTO gears for a small multi-purpose cultivator using the ISO 6336 and Miner’s rule. The torque measurement system was constructed with torque sensors to measure the torque of a engine shaft, a measurement device to acquire sensor signals. Conditions of field test were conducted at two transmission gear stage (1st, 2nd) and two PTO gear stage (1st, 2nd) with 100 mm working depth on the field with similar soil conditions. Results: The average torques on the engine shaft for PTO gear 1st, 2nd at transmission gear 1st were 11.64, 18.05 Nm, respectively; the same for PTO gear 1st, 2nd at transmission gear 2nd were 17.67, 22.98 Nm, respectively. Discussion: As gear selection is higher, the torque on engine shaft tended to increase and the fatigue life of PTO gears are reduced. Conclusion: Therefore, farmers should carefully determine the gear selection of the cultivator by considering the load and durability of the machine.