Conventional TOFD technique uses the longitudinal diffracted wave to locate and size the flaw. However, owing to the superposition of the lateral wave and the deviation between the welding and the axis of main acoustic beam, there is an insensitive region near the surface, resulting in missing inspection. In order to solve the problem above, an analytic method named as S-wave TOFD is presented based on shear wave diffracted from defect tips. The characteristic of sound propagation in S-wave TOFD method, the detection principle and the method of quantitative calculation are illustrated in detail. Through the experiments of artificial defects detecting, the result shows that the S-wave TOFD method can significantly improve the detection sensitivity and precision for the shallow buried defects for that it can effectively identify the near surface defect with buried depth of about 2mm and the calculated error of the height and buried depth of defect is less than 1mm.