The servo control unit is the core component of a certain optoelectronic system. Based on analysis to working principle of the optoelectronic system and testing requirements of the servo control unit，we proposed a scheme for design the software/hardware of the testing platform for the control unit. In order to verify the mechanical structure stability of the simulated load and the accuracy of DC motor control system, virtual simulations to the pitch and azimuth mechanism of simulated load were accomplished by using Adams and Matlab/Simulink. The scheme design of the testing platform and the virtual simulation analysis to the simulated load can provide a reliable basis for further study.