To enhance the detection capability of small defects within curved components using ultrasonic phased array, this paper proposes a phased array focusing delay method tailored for curved structures. In this paper, the Rayleigh integral mathematical model for the linear phased array focusing field is established, and the directional distribution of the sound field is analyzed. By applying Snell’s Law, the focus delay rules for inclined and curved components are derived. Compared with the traditional iterative traversal algorithm, the proposed method improves the calculation efficiency of the delay rule, reduces the influence of interface structures on the curvature of the scanning sound beam’s wavefront, thereby fully leveraging the detection advantages of linear phased arrays. In the established curved component simulation model, the delay is applied sequentially to each element based on the proposed method. Simulation results confirm that the sound waves can be effectively focused at the present location, and the computation time is reduced by approximately 70% compared to traditional iterative methods. Furthermore, practical detection experiments were conducted using a ring-shaped steel test block with a Φ0.3 mm blind hole. By comparing the B-scan images and A-scan signals before and after applying the delay rule, experimental results show that the proposed method significantly improves the signal-to-noise ratio and imaging quality in detecting small defects in curved components.