In response to the demand for the resource utilization of residual films in Xinjiang and the challenges of shredding and separating existing film residue mixture, a combined shredding and separation device featuring a rolling knife and axial flow drum was designed. This device can facilitate the feeding and shredding of mixed residual films, as well as the separation of residual films and the crushing of cotton stalks. Utilizing dynamics and kinematics, the processes of feeding, shredding, and separation were analyzed, revealing the main factors and parameter ranges that affected the efficiency of shredding and separation. The experimental factors included the feeding roller speed, shredder speed, and separation drum speed, while the evaluation indicators were the residual film content in the residual films, the residual film content in impurities, and the qualified rate of cotton stalk crushing length. Single-factor and Box-Behnken response surface experiments were conducted by using Design-Expert software, followed by variance and response surface analyses to clarify the impact patterns of experimental factors and their interactions on the experimental indicators. Through multi-objective optimization of the established second-order polynomial response surface model, the optimal operational parameters were determined: feeding roller speed of 20.94r/min, shredder speed of 335.78r/min, and separation drum speed of 282.38r/min. Experimental validation with these optimized parameters yielded residual film content of 91.26% in the residual films, 7.22% in impurities, and qualified rate of 93.78% for cotton stalk crushing length, thereby meeting the operational requirements for shredding and separating film-mixed residues.