An improved measurement algorithm,based upon the theory of two-way time transfer(TWTT),is proposed to measure satellites with high speeds.The algorithm makes theoretical analyses and corresponding deductions on a relative motion model of two satellites,and eliminates the measurement error caused by the equipment delay when a satellite moves at a high speed.Theoretical analysis and simulation results demonstrate that in comparison with the conventional TWTT algorithm,the proposed algorithm can significantly enhance the measurement accuracy of the inter-satellite ranging and time synchronization,and the algorithm is more effective with the relative velocity between the satellites and transmitting delay becoming larger. An improved measurement algorithm, based upon the theory of two-way time transfer (TWTT), is proposed to measure satellites with high speeds.The algorithm makes theoretical analyzes and corresponding deductions on a relative motion model of two satellites, and eliminates the measurement error caused by the equipment delay when a satellite moves at a high speed. theoretical analysis and simulation results demonstrate that in comparison with the conventional TWTT algorithm, the proposed algorithm can significantly enhance the measurement accuracy of the inter-satellite ranging and time synchronization, and the algorithm is more effective with the relative velocity between the satellites and transmitting delay becoming larger.