In LEO satellite communication system, the high speed movement of satellite makes the AER (Azimuth, Elevation, Range) characters of inter-orbit adjacent satellite changing deeply. So, the topology optimization of LEO satellite becomes a big challenge to OBP (On-Board Processing) satellite system. In this paper, the Polar global coverage satellite constellation is studied. The inter-orbit and intra-orbit ISL (Inter-Satellite Link) are analyzed to optimize the Polar satellite constellation topology. According to the ISL characters, the topology control strategy based on optimal polar boundary is proposed, and computer simulation results are given for this satellite constellation.