The dynamic characteristics of the cotton stalks during the cutting process were analyzed, and the key parameters (e.g. the number of teeth, rotating speed and cutters gap) of multi-edge toothed cutting device that affect the cutting of cotton stalks were determined. Based on the designed cutting device, central composite design method and regression variance analysis method were applied to build the distributed characteristic model of the cotton stalk length in the mixture of mechanically recovered residual films and impurities after shredding, and the optimal combination of parameters was obtained. The influence law of the key parameters as well as their obvious interactions on the distribution characteristics of the cotton stalk length was analyzed, and the optimal combination of parameters of the cutting device was obtained. The average error between the physical test value and model predicted value under the same condition was 7.54%, which indicated that the test results were basically the same as the model prediction.