Abstract: This paper, based on the analysis of the principles and methods of the ultrasonic testing of bolts and combining with the actual situation of ultrasonic phased array inspection of bolts in service, aims to discuss the main factors affecting testing results via the analysis and comparison of the phased array inspection for bolt samples. The influence factors, which include sector angle selection, detecting position, equivalent reflector size and equivalent reflector position, are discussed and therefore hoped to become the basis for formulating the procedures of ultrasonic phased array inspection of bolts.