The invention discloses a turnplate type crab weight sorting device and method, and relates to the field of weight sorting. The device comprises a turnplate, a controller and crab storage boxes, wherein the turnplate comprises slots which are arranged in a surrounding manner, a baffle is arranged between two adjacent slots, and baffles are arranged at inner and outer end faces of each slot; movable trays are arranged at the bottom of the slots, and a weight sensor arranged under each movable tray is used for detecting the weight of a crab on the movable tray; the inner edge of each movable tray is a fixed end, and a turnover device is arranged at the fixed end of each movable tray to control the respective movable tray to turn over along the fixed end; the controller is respectively connected with each weight sensor and turnover device, is used for receiving the weight information transmitted by the weight sensors and determining the time for turning over the corresponding turnover device according to the weight information; a rotary motor is arranged at the center of the turnplate to drive the turnplate to rotate; the crab storage boxes are placed under movable trays correspondingly, and are used for collecting falling crabs after the movable trays are opened. According to the device and method, the weighing accuracy and sorting efficiency of crabs can be improved.