To increase the channel efficiency, most of the Low Earth-Orbital satellite (LEOs) systems use the multibeam antenna and reuse the available channels. But in such systems, a beam handover occurs very frequently and a dropping probability becomes very high compared with the one beam systems. In this paper, we propose the nondropping handover and channel allocation scheme in the above LEOs systems. In the proposed scheme, we allocate an extra idle channel for a new call. Because of the predictable change of channel reuse distances, each user can always use the same channel as before. Furthermore, we proposed some cost functions used by channel selection and channel reassignment. For comparison, we show the lower bound of blocking probability by maximal complete dependent set (MCDS). We confirm that the proposed channel selection scheme improves the system performance by computer simulation.