According to the problems of field plastic film pollution with film mulching of double rows on a big ridge cultivation pattern of potato in northwest arid area of China, the canvas belt combined operation machine for potato harvesting and plastic film collecting was designed, which had synchronous implementation function of potato harvesting and plastic film collecting. Based on design and calculation analysis of key operation parts for prototype, the operation parameters of anti-twining device, canvas belt transporting film device and floating curl-up film mechanism were determined. The related experimental factors and their range of values were determined which affected the plastic film collecting ratio of the combined recovery machine. The Box-Behnken experimental design with four factors and three levels was performed, the mathematical models between the key parameters such as operation machine speed, film-curling driving roller rotating speed, transporting film axis rotating speed, transporting film sheet dip angle and plastic film collecting ratio were established, and then the effects of various parameters and their interactions were analyzed as well. The test results showed that effects order of four parameters on the plastic film collecting ratio were as follows: film-curling driving roller rotating speed, operation machine speed, transporting film axis rotating speed and transporting film sheet dip angle. The optimal working parameters were combined operation machine speed of 0.72m/s, film-curling driving roller rotating speed of 303r/min, transporting film axis rotating speed of 499r/min and transporting film sheet dip angle of 29°. Confirmatory tests showed that the average value of the plastic film collecting ratio was 92.1%, compared with before the optimization it was dropped significantly. At the same time, under the operating parameters the obvious ratio of potato was 96.6% and the injury ratio of potato was 2.2%, which were up to the relevant work quality evaluation specification requirements.