A kind of Rekeying Algorithm based on Orbital Cluster (RAOC) is proposed in the Low Earth Orbit (LEO) satellite network. The LEO satellite network is divided into different clusters according to the characteristics of the LEO satellite network in RAOC. The rekeying process is carried out by the initiating node of the LEO satellite network and the head nodes of the clusters. Rekeying lock is introduced to ensure consistency of the rekeying. The simulation results indicate that RAOC can accomplish the rekeying automatically compared with ground-based TTC(Tracking, Telemetry and Command) algorithm and space-based TTC algorithm, and the rekeying efficiency is improved by RAOC.