Abstract: In order to detect the fatigue damage of high-strength bolt in steel bridge in time and accurately, the fatigue crack simulated by manual grooving damage in 10.9S grade M30 high-strength bolt commonly used in steel bridge were detected by phased array ultrasonic technique. The effect of end face under detection, damage degree and damage location on fatigue crack damage identification were studied. The test results showed that using screw thread end as detection face could effectively reduce the undetected rate and miscalculation, and the detection accuracy is better than that of another end. The phased array ultrasonic has a good detection accuracy for the manual grooving damage greater than 1mm in bolt holding length, and could identify the damage location with the relative positioning error within 7%.