In order to demonstrate the validity and the benefit of the closed-chain kinematics of four-link motional method for the gait of wall-climbing caterpillar robot, the mathematical model and the relation of kinematical parameters were built. The caterpillar robot can climb on vertical wall by coordinated rotation of one active joint and three passive joints. To testify the availability of the closed-chain kinematics of four-link method, a prototype of wall-climbing caterpillar robot with three kinds of adhesion modules was designed. A successful wall-climbing experiment confirms the principles of the closed-chain kinematics. The results show that the basis for selecting driving joints was reasonable and that the adhesion module can produce powerful adsorption force with small weight and volume to ensure the safety and reliability of wall-climbing.