Abstract: In order to solve the problems of high labor intensity and low efficiency in manual identification and picking up dead chickens in large-scale farms, this paper designed a 3-joint and 4-finger end-effector of the robot based on the underactuated theory, taking the cage broilers aged 3-7 weeks as the operating object. Based on the measurement of body size and mechanical properties of broilers, the mechanical finger parameterized model and the broiler finger model were established by ADAMS, and the mechanical finger structure was optimized according to the objective function,design variables and conditions.The optimization results showed that the objective function increased by 28.6%. The end-effector motion simulation grasping experiment was carried out for broilers aged3 weeks and 7 weeks. The results show that the manipulator had stable transmission and good grasping effect. The robot hand test prototype was used to grasp the dead chickens. The average success rate of the robot grasping the broilers within 30 minutes of death was 88.3%, and the average success rate of the broiler chickens beyond 30 minutes of grasping death was over 96.7%, and the average grasping time was over 96.7%, It was 32 s, and the manipulator had higher working efficiency and reached the design goal.