A number of analyses and designs were carried out for the class II. six-pole mechanism in the bull head planer. The mechanism design scheme with the maximum pressure angle of the mechanism as the minimum value was determined; The motion analysis of the mechanism was carried out by the vector equation analysis method. According to the requirements of the working speed of the planer during planing processing, a mathematical model of the optimization design with the smoothness of the working speed of the planer as the objective function is established, and the optimization design is carried out by the composite shape method. The results of the example calculation show that the speed and smoothness of the planer in the working stroke of the optimized design of the class II. six-bar mechanism are significantly improved, which provides an effective design method for improving the working quality of the class II. six-bar mechanism in the bullhead planer, and this method also provides a theoretical basis for the optimization design of other reciprocating motion mechanisms.