Abstract: The position of the 3-RPS parallel robot is analyzed by the method of coordinate transformation and the position closed-form method. Based on matlab, the simulation model of this robot is established. With the reference input in different condition, the simulation comparison is made through setting the parameters of the PID controller in reason to simulate. The results show that in different reference input condition the changes in the position of the moving platform are almost identical, the effect of PID control leveling is realized and the deviation between the actual output of drive shaft displacement and the reference signal fluctuates in the allowable range, the control effect is obvious. This provides the information for the study of automatic leveling to the parallel robots.