This study provides a practical method regarding the development of a complete self-diagnostic technique for monitoring the bearing damage of bolted composite or metallic joints. The basic concept is based on making BG (Bolt Gauge) measurements that has been proposed in earlier work [1,2]. That is, bonding a strain gauge onto the surface of bolt head to monitor the bolt strain changes that would identify bearing damage. Extensive tests using double lap bolted joint specimens are performed to verify the health monitoring technique, including the effects of the bolt clamp-up, material response, joint geometry and loading history. The results have shown that the bearing damage detected by BG measurements agreed well with acoustic emission (AE) measurements. Finite element analysis is performed to discuss the monitoring mechanisms.