Abstract: Due to the complexity of the mathematical description of robots, kinematic and dynamic analysis of robots is quite difficult. Therefore, most quadrupedal walking robots adopt model-based control methods, which require modeling of the robot itself and its surrounding environment. Under complex models, the real-time performance of controller calculations is difficult to guarantee, resulting in greater control difficulty and limiting robot performance. This paper uses the SimMechanics toolbox in MATLAB to build a computer model of a quadrupedal robot and simulates the motion of the robot's legs and torso. Through simulation, the rationality of the model is verified, and simulation diagrams of the robot's leg joints and torso motion are obtained, providing a basis for further analysis of the robot system's performance. Keywords : Quadrupedal walking robot; SimMechanics tool; Model; Simulation 1. Introduction The mechanical structure and drive of a quadrupedal robot directly affect its movement speed, power consumption, and load. Since the leg mechanisms of quadrupedal robots are mostly open-chain mechanisms, the robot has many joints and therefore many degrees of freedom. To achieve stable and rapid walking, the coordination of multiple joints is required, which brings difficulties to the kinematic and dynamic analysis of the robot. While kinematic analysis can yield results through spatial transformations of the mechanism, dynamic analysis involves more variables and more complex formula derivations, making mathematical calculations for robot dynamic analysis more difficult. This paper first conducts kinematic analysis of a robot in a straight-line walking gait. Based on the results, a robot model is built using the SimMechanics toolbox software in MATLAB. Model simulation is then used to obtain motion simulation diagrams of the robot's body and legs, laying the groundwork for further research. 2. Motion Analysis of a Quadrupedal Walking Robot Full text download of SimMechanics model building for a quadrupedal walking robot