The thermal conductivity of hydrogenated amorphous silicon (a-Si：H) film was measured using platinum metal as heating resistance. The films are prepared by plasma enhanced chemical vapor deposition (PECVD) and the thickness of them is in the range of 300—370nm. The dependence of thermal conductivity of the films on substrate temperature was studied. The influence of substrate temperature on the growth rate of a-Si：H films was obtained by spectra ellipsometer (SE). Fourier-transform infrared spectrometer (FTIR) was used to characterize the infrared spectra of films deposited on KBr substrate. The thermal absorption duc to vibrational mode of Si-H bond decrease the thermal conductivity of the films. Kinetic theory was used to analyze the result that the thermal conductivity of the films increases with the increasing of mean temperature. The effects of phonon propagation and free electrons displacement on thermal conductivity was also compared.