In this paper, a new method using reflective pulsed thermography to measure defect depth, thermal wave reflection coefficient and thermal diffusivity is presented. First, a brief description of the pulsed thermography in terms of theoretical background and quantitative measurement is given. One stainless steel 304 structure machined several flat-bottom holes in which it is filled with different materials are used as experimental sample, the measured results of defect depth, thermal diffusivity and reflection coefficients at defect interface under different conditions are given. The agreement between the results obtained by using pulsed thermography and the value presented in the literature or measured by other techniques appears satisfactory within errors of 5%, and possible reasons for affecting the measurement precision are discussed.