Abstract: According to the characteristics of mixed constellation of BeiDou system after adding LEO enhanced constellation，in order to meet the major inter satellite link business requirements of the next generation navigation constellation，a hierarchical planning scheme for inter satellite link planning of hybrid constellation was proposed，and priority was given to the establishment of topology for MEO，LEO and MEO LEO of laser inter satellite link.A grouping topology planning algorithm for TDMA was proposed based on the topology，and two improved routing algorithms were proposed for hybrid inter satellite networks in navigation constellation.Simulation and planning of the hybrid system inter satellite link were carried out，the correctness of the hybrid network planning method was proved，and the data transmission efficiency of the hybrid network in three typical navigation business scenarios of LEO monitoring data backhaul，inter layer data transmission and navigation information injection was verified.The results show that the delay of LEO monitoring data backhaul and continuous system node navigation information injection is less than 1s.There are 5～8 inter layer intersatellite links for 94% of the time，and the TDMA node can complete the navigation information injection in 12s for 92% of the time，which provides reference for the planning and design of the next generation navigation system.

Key words: navigation constellation, augmentation based on LEO, laser inter satellite link, topology planning, routing algorithm