Unstable operation performance of mechanism for collecting plastic film results in low rate of collecting used plastic film. A crank-rocker mechanism for collecting plastic film was presented. The geometry and mathematic models of the proposed machine were built for simulating, analyzing and optimizing the work mechanism, then the working requirement for picking-up and removing the used plastic film was met. Field experiment showed that, the working efficiency of machine was higher than 0.4hm2/h, and the rate of collecting used plastic film was 88.5%. Basically, no operation wound problems were found during the whole experiment.