The operational ability and mobility of astronaut in spacesuit is an important data for evaluation of the spacesuit, and to know it before use is also a basic data for the design of space station and spaceship. For this reason, mechanical arms were developed to measure the mobility and operational ability of astronaut in spacesuit. However, the mass and motion inertia are always influence the measuring system. This paper studied the dynamics characteristics of the mechanical arms. Dynamics model of the mechanical arms were setup and solved by MATLAB. Angle, angular velocity and angular acceleration of each joint were analyzed. The simulation supply a good basis for the development of the measuring manipulator, and it is helpful for the high accurate measurement.