A model rotary knife roller based on similitude method was designed with 1/2 real size to study the performance of the double spiral rotary tillage and stubble-mulch roller machine while it till in paddy soil. A test platform of 1/2 size model roller for torque based on LabVIEW was designed. The indoor soil bin test of the 1/2 size model roller was conducted and its working torque was chosen as evaluation indicator while moisture content of soil, forward speed, rolling speed and tilling depth were selected as influential factors. The results of single factor tests showed that torque increased with the increase of forward speed and tilling depth, and decreased with the increase of knife rolling speed in experiment range. The result of L18(37) orthogonal test showed that the influencing sequence on the knife roller torque from significant to common was soil moisture content, tilling depth, forward speed of the test platform and knife rolling speed. Soil moisture content, tilling depth and forward speed of the test platform affected significantly, while knife-rolling speed did not. It will provide a reference for the optimizing structure parameters, motion parameters and power choice of double spiral rotary tillage and stubble-mulch roller.