At present, the meat of Mytilus coruscus is usually obtained by thermal processing, but fresh meat could not be obtained by this method. In order to obtain the meat of fresh Mytilus coruscus with half shell, according to its biological characteristics, the basic parameters of Mytilus coruscus such as scar area of posterior closed shell muscle and shell length were determined by statistical analysis method, and the relevant parameters of the force needed to pull off the posterior closed shell muscle column were determined by mechanical experiments, thus a device for shelling Mytilus coruscus was developed. The device consists of worktable, support arm, pneumatic cylinder, shell-opening cutter, vacuum sucker, Mytilus coruscus fixed platform and conveyor belt. Through finite element analysis, it is determined that the optimum cutting edge width of shell-opening cutter is 9mm and the applied force on the cutter is 900 N. The device can effectively improve the shell opening efficiency of Mytilus coruscus, reduce the labor intensity, and meet the needs of processing enterprises.