The siting error and L>O>P> of short distance navigation positioning system have been analyzed. The relationship between positioning precision of navigation system and detecting probability of fighter for intercepting is established. The curve of relationship on the detecting probability with the navigation system operating range and the explorative distance of airborne radar is set up for the first time. The influence on the intercepting effectiveness of fighter by the navigation system is presented. So it is of great value to tactic research and application of navigation system.