Aimed at 6-DOF modular serial manipulator, forward kinematics was established and an inverse kinematics calculation method was proposed. To the structural characteristics of the manipulator, a forward kinematics model was conducted by using the DH method to describe the workspace. In the process of solving inverse kinematics, because the independent irrelevant variable equation can not be found by the pure algebra method, the geometry method was employed to solving the inverse kinematics of the first three joints, and the last three joints were solved by using algebra method. The complete analytical solution of the inverse kinematics was acquired by giving the combination principle of solutions. In order to meet the need of programming and actual control of robot system, the correctness of forward and inverse kinematics was validated by software developed based on MFC of VC++.