Abstract: In the present paper, a nonlinear dynamic model of free-floating dual-arm space robot systems is presented based on the Lagrange method, and the dynamic model of an object is presented in terms of the Newton-Euler method. Based on the results and closed kinematic chain constraints, the dynamic model of a synthetical system is obtained, and the control problems for the object to track the desired trajectory in the workspace and adjustment of interactive forces due to the interaction between the object and the end-effectors are discussed. Because of the high structure complexity and the parameter uncertainty of such systems, the scheme of variable structure sliding-mode compensation control with better robustness to uncertainty and disturbance is proposed to track the desired trajectory of an object, and the corresponded scheme of internal force control is proposed synchronously. Therefore, the object position and internal forces can be regulated simultaneously. The effect of the controllers is testified by computer simulation.