Abstract: This paper discusses the key technologies of anti-torpedo torpedo (ATT) weapon systems and the subsystems including overall design, homing, control, fuze and warhead, and presents technical requirements for the main subsystem s. The ATT weapon systems should equip active and passive sonar in order to improve interception probability. A guidance method adapted to ATT intercepting trajectory is presented. The principles to determine homing range and homing searching sector are given. The maximum allowable angular rate of ATT must no less than 80 degree each second and the tracking error for instruction must be no more than 15 percent with in one second in order to get high maneuverability and fast response to control system. The issues about fuze and warhead subsystem that ATT should adopt active acoustic fuze and damage radius must match with average miss distance are also discussed.