Since the objective existence of errors and interference in guided bomb practical delivery processthe accessible region calculated by the ideal trajectory model cannot ensure the necessary hit probability. The influence of some typical errors and interference to the hit probability of guided bomb was studiedthe substaintial characteristic of accessible region was described in the view of hit probability distribution via MonteCarlo target practice simulation in integrated interference.A quantitative reduction method was proposedwhich could increase the hit probability of guided bomb in practical delivery environment. Simulation showed that the method is simple and has high generality and feasibility.