A set of real-time algorithms for inverse kinematics of all type of 6R robots is proposed. The general algorithm obtains 16 inverse kinematics solutions in total for general 6R robots based on vector operations and eigenvalue-decomposition of a 16 order target matrix. The closed-form algorithm selects proper kinematics equations directly and solves for the joint variables analytically. The obtained results are employed by the combined algorithm as the initial values in the iterative Newton-Raphson method for finding the exact solutions of the inverse kinematics, which can be used for 6R robots that approximately meet the requirements of the closed-form algorithm or the general algorithm. Experimental results show that the proposed set of algorithms solves the inverse kinematics problem of 6R robots with any geometry configuration in 2.03 ms, and provides effective solutions for the inverse kinematics problem of 6R robots applied in strong real-time systems.