Abstract: Because of the bad working environment of the core-making robot in foundry, the stability of the robot grasping sand core is poor, and the problems of core dropping and core pinching often occur. In view of the above problems, a mathematical model of the system with gripper, air pressure and mechanical vibration is established, and the stability of the system is determined by the distribution method of the poles of the higher order system on the splane. Under the condition that the pole value of the higher order system is invariable, the influence of the zero value on the stability and oscillation attenuation time of the system is observed by changing the zero value of the system. Using the pzmap and impulse functions of Matlab to simulate the different responses of the system to zero, pole distribution and zero value respectively, and using the simulation results and field tests to optimize the parameters, the results show that the stability of the core-making robot can be optimized by using a gripper with stiffness and flexibility of 1/2 each.