Abstract: The field straw chopper with throwing cotton-stalk adopting high speed rotating flail knife can chop cotton-stalk, throw it into a certain height and distance, at the same time it can clean up the cotton-stalks on the film. So it can create a condition to separate cotton-stalk from the film on recollecting reminder film with machines after autumn and recollect cotton-stalk to raise cattle and sheep. Through underlying theory analysis and experimental study, the basic structure and main parameters were determined, and the rational proportioning relationship between knife-roller speed and forward speed of unit was obtained by experiments, at the same time, the speed of flail knife and other main technology parameters were analyzed in more detail, and the height of chopped rootstalk was lowered. The experimental results prove that the performance of the sample machine was improved. It can meet the demand of the cotton-stalk field straw chopper after autumn.