Abstract: The synthetical error about the firepower control system made up of principle error,diffuse error of trajectory,present error of aviator,middle wind and etc.manifold error.In order to assess principle error of system,must eliminate else error from result of bomb release.If the method of outer trajectory is adopted,the period of flight-test is long and a great of manpower and resource are used.The assess method about the precision of firepower control system by the system analogy is proposed in this paper.The else error are obtained form the already critical system and are eliminated.The result of theoretics and the result of bomb release have proved that it is a effective and economical assess method about the precision of firepower control system.A new way has explore about assess method for same airplane using different firepower control system.