Three-DOF air-bearing test-platform is the key test base of simulating the satellite attitude motion for simulating the satellite emulation effective, so as to simulate the torque-free environment in the space. 3-DOF air-bearing test-platform disturber moment is analysed. When there is a shift between the gravity center and the rotary center, the static unbalance appears. While a shift exits between main inertia axes and rotary axis, the dynamic unbalance appears. In addition, the principal and procedure of balancing a 3-DOF air-bearing test-platform and the technology of manual and automatic balancing it are discussed. The equations of kinetics are derived. At last a lot of methods are used to measure the static unbalance moment and disturber moment in order to supply satellites' attitude motion with a model of availability, precisions and efficiency.