The computation equation and design criterion of real effective navigation ratio of homing control trajectory in PN homing guidance system were given.

The guidance, navigation and control(GNC) system, the brain system, is the one of the key systems of RLV. In this paper the mission requirements and system structure are first studied.

Quality is a permanent problem. It is not only a lifeline of military products, but also a key problem of research and production in navigation, guidance and control system domain.