The structural parameters and the kinematics parameters of the knife roller, a core part of the machine for chopped and reclaimed field straw, were discussed through theory analysis and experiments. The arrangement method of flail knife, the minimal gap between the edge of knife and the ground when the machine in static state, the rotate speed of knife roller were determined. The study provided a scientific basis for developing the machine that can be utilized for the purpose of mulching or reclaiming after the field straw was chopped, although fan has not been installed in the machine.