The morphological properties of the bay scallop affects weight properties were analyzed quantitatively, by determining the shell length as a key trait for grading work. By combining the characteristics of the physics properties of the bay scallop, a V-wheel roller grader was designs. and Slid-works was used to build a dimensional machine model of V-wheel roller grader. The results showed that the design of V-wheel roller grader was reasonable and the structural was novel, can achieve high efficiency and precision grade scallops.