A novel method using motion skeleton and behavioral modeling in Pro/Engineer to design a motion mechanism is proposed in this paper. With this method, intuitive kinematical simulation system of a motion mechanism can be set up quickly and mechanism dimensions can be determined automatically. Deployment mechanism, as one kind of motion mechanisms, is often used to stretch out solar panels or antennas in spacecraft. This method is feasible and reliable to determine the dimensions of a six-bar-linkage deployment mechanism for stretching satellite antennas. Simulation results are obtained with kinematic simulation software Pro/Mechanism. The feasible designing solution to the six-bar-linkage deployment mechanism meets high position precision requirements accurately.