Based on the requirement of hitching system for a tractor mounted farm implement, a mathematical model was developed for optimization design of the hitching parameters of a four bar linkage mechanism. The lowest positions of the transient velocity center of the tractor and the working implement were taken as the objective function of the model. The fmincon function in Matlab was adopted to realize the optimization work. The design and computation results for the plough (model 1L-430) by the improved method proved to be quicker and with a higher precision than those by the conventional drawing method.