In the space docking experiment, a new spatial indexing manipulator was designed based on the theory of biaxial inertia simulation. A speed increasing mechanism was used to simulate the large inertia load in the station. The dynamical equations of the system were built by Lagrange method. The device structure was determined by the inertia coupling parameters of the rotational joints. The indexing and speed increasing mechanisms of the manipulator constitute an arm model which was proved to be unique in the trajectory. A kinematics simulation was made for the device by SimMechanics and ADAMS. The results show that using a small device can simulate a large inertia loads．Given the initial conditions, the translocation and brake in the device can be finished well. So，the spatial indexing manipulator is proved to be feasible and applicable.