Aiming at the problem that traditional non-destructive testing methods are difficult to detect rail head damage under different radii, a phased array ultrasonic testing method based on the complex curved surface damage of rail heads is proposed. For the complex structural features of the rail head, a phased array ultrasonic static focusing detection scheme is formulated; based on Fermat′s principle, a calculation method for the delay time of the phased array ultrasonic synthetic beam under different radii of the rail head is proposed; a finite element simulation model is established to analyze the propagation characteristics of the phased array beam in the rail head; based on the discontinuous Galerkintime-domain(DGTD) method, a phased array ultrasonic dynamic response simulation model of the rail head is established and the A-type signal characteristics of different defect positions in the rail head are analyzed. Finally, phased array ultrasonic experiments were conducted on defects pre-embedded at different positions of the rail head and defects with a diameter of 1 mm can be accurately detected. The results show that the optimal average signal-to-noise ratio for defect detection in the central area is 22.97 dB and for the near-surface area with a larger rail head curvature, it is 17.16 dB. Compared with the traditional single-probe ultrasonic testing method, this method increases the testing speed by approximately 40%. Compared with the conventional phased array method that has not been optimized for the rail head′s curved surface, the average defect detection signal-to-noise ratio at the center of the rail head and in the large curvature area near the surface has been increased by approximately 10 and 12 dB respectively.