To investigate the ability of photothermal radiometry (PTR) testing on the subsurface of metal materials, the amplitude and phase of thermal wave generated from a double layer material which is excited by intensity modulated laser are analyzed theoretically. Besides, the PTR signals of stepped steel samples, aluminum/steel samples with blind hole array, and steel samples with blind hole filled tin are tested in experiments. For the aluminum samples with blind hole array with diameters of 2.5, 2.0, 1.5 mm and hole bottom thickness of 0.2, 0.4, 0.6 mm, the PTR phase distributions obtained by the experiment show that the diameter of the blind hole and the hole bottom thickness are distinguishable. For the steel samples with blind hole array, the PTR phase distribution before and after the blind hole filling with tin shows a certain difference. The experimental results show that the PTR detection of the focused spot can detect the stoma defect in aluminum or steel. The depth of the stoma defect should be less than or approximately equal to the thermal diffusion length of the surface material, and the cross-sectional area of the stoma defect should be approximately equal to or greater than the spot.