Quantum satellite communication can meet the requirement of quantum mobile communication among sailing, aviation field with longdistance and extensiveness communications, and onboard switching is one of the key techniques in quantum satellite communication. Based on the onboard switching technique in low earth orbit (LEO) quantum satellite communication, a novel algorithm is proposed that is terminal measuredistance method. By using this algorithm, the distances between terminals and its adjacent cell center are measured, and then the distances data are uploaded to the current satellite system, finnaly the satellite system compares the distances and determines whether to handover or not. Mathematical analysis and simulation results show that the proposed algorithm has high reliability, is easy to operate, and can smoothly switch between the different satellites.