Abstract: This paper presents a new kinematic modeling method for a wheeled mobile robot operating in a 3-dimensional complex terrain with entrenchments, steps, and slopes. The new method is called Tangent Planes Combination Method(TPCM). The main idea of the TPCM is to form a composite kinematics model for a robot operating in rough terrain combining different kinematics models of the robot on different slopes at different time. This kinematic modeling method has characteristics, such as simplicity, a controllable accuracy of a robotic kinematics model, etc. By use of TPCM the forward and inverse kinematics models for a five wheel articulated lunar robot(FWALR) operating in rough terrain was found. Thus, the FWALR robot has a base to control its movement in a 3-dimensional complex terrain.