Abstract: This paper briefly describes the principles of balancing and correcting for low-speed spinning satellites that work as rigid rotor on ver- tical dynamic balancing machines provided with hard supports.It presents a correct formula,determining methods and determining results for minimum achievable residual unbalance of YLP-1 type vertical dynamic balancing ma- chines with hard supports.It concisely gives the error source analysis and data processing in the process of satellite balancing,and derives the formula for calculating the residual unbalance a which determines the final balacing accu- racy of rigid rotors.It also presents two groups of data of the tests for balancing returnable remote sensing satellites.Flying tests have proved that the expected design object is achieved.