Based on the principle of phase difference, the actual power consumption of the rotary tillage and stubblemulch knife roller in midseason rice straw field was tested by using magnetic torque sensor. The processing procedure was based on LabView. The system was calibrated on the experiment bench. The results showed that accuracy was lower than 5%. The results of field testing showed that the tillage depth of the machine and the rotate speed of axis greatly influenced the power consumption. The better operating status were as follows: operating power consumption of the first tillage with 55mm of depth and 310r/min of roller speed, its average was 7.13kW; operating power consumption of the second operations with 110mm was 7.59kW, the ratio of straw returning was higher than 95%.