Abstract: To solve problems of ‘over-maintenance’ and ‘less-maintenance’ existed in phased array radars, the condition based maintenance (CBM) technology has been proposed in this paper. It mainly includes the following items listed as the multi-signal flow based fault diagnosis, the health comprehensive estimate, the condition tendency prognosis, the logistical policy, and the maintenance autobiography management during the total life period. The CBM mode has the tremendous and significant engineering value in achieving the precise preventive maintenance for phased array radars, which can further improve the availability of radars and the self-maintenance capability of army.