Abstract: Since the phase was sensitive to noise in pulsed phase thermography technique, the data of temperature obtained from the thermal wave experiment was fitted in order to reduce the noise influence. The fitting result indicated that piecewise fitting could get better fitting functions, consequently could get phase curves with low noise and a clear phase image after Fourier transform. Another advantage was that data could be represented by coefficients of fitting functions, and the storage of data could be greatly reduced. The effect of the value of sampling frequency and window width on phase through fitting was analyzed by using interpolation methods.