Abstract: In order to relieve the working intensity of field-snail shelling and washing, a kind of field-snail washing machine with simple structure and convenience operation was designed. After analyzing the dimension of crank rocker mechanism for vibrating screen and maximizing the drive angle for optimization object, it is obtained that the length of crank, connection rod and rocker are 8 mm, 180 mm and 220 mm, respectively. Through movement analysis of mechanism and experimental study, it is concluded that the rotation speed of crank is approximately 600 r/min, the threshing rate can reach 96%.