By studied a three degree of freedom (3-DOF) parallel platform, a Stewart parallel platform center of gravity stability analysis method is presented, and its Simulink simulation is carried out. First, a three dimensional (3D) model of 3-DOF Stewart motion platform was built in 3D Creo modeling environment, and then input to Simulink through Creo to generate cooresponding Simmechanics modules, including the three motion branches, each branch consisted of the hinge, electric cylinder, drive rod, moving and fixed platform, and etc. Next, in the Simulink simulation environment, the three branched motor modules was added with drive module, and then the Fcn function programming was used, so that the drive module on the machine to drive the motor, resulting in a different amount of the drive lever to achieve a predetermined trajectory of the moving platform. Finally, in the Simulink environment programming is to achieve a rotation of platform for a cycle at a certain angle formed between the two planes of platform and water level, while the center of gravity is stable of the 3D Stewart motion platform’s own special movement.