Abstract: Direct attack with satellite guided weapon is one of the most important means for precision ground strike. The direct attack operation needs high precision target position, which cannot be satisfied by conventional positioning methods. The relative GPS guidance is the key technology for airborne satellite guided weapon direct attack. This paper presented the direct attack concept of satellite guided weapon, and analyzed the errors of relative GPS guidance technology. The errors were induced by relative GPS position and airborne sensor relative position. The position precisions of them were analyzed. The simulation results indicated that the overall error of the relative GPS guidance was less than 7.5 m, which satisfied the requirement for the satellite guided weapon direct attack.