For guiding the reliability design about fire control system in design phase, aiming at mean time between failures (MTBF), put forward an applied method about reliability allocation. Through establishing basic reliability model, it adopts the combined method of project weighed and expert grading to direct the reliability allocation of fire control system. The allocation data is availability and feasible and according with the MTBF about fire control system. The result shows that the method can guide the reliability allocation of fire control system in design phase availably.