Based on rectangle circulating chart method, a seed melon pulp-excavated machine was designed. Improved swinging cam was used for feeding melon mechanism, a 2-round pin and 4-grooved wheel mechanism were chosen to realize precise indexing motion of a plug melon saddle, and flat-bottom tappet disc cam mechanism with improved rod gear mechanism was used for lifting tool saddle. The orthogonal experiment was done and the optimum parameters of digging was discovered as follows: the type of digging tool is hemicycle, the speed of digging tool is 240r/min and the installation angle of digging tool is 15°. Replicated tests showed the cleaning rate is more than 98%, grain seedless rate is more than 98%, loss rate is less than 2% and broken rate is less than 1%, respectively.