Abstract: The surface of transparent covering materials with low heat resistance is the main channel for heat transfer and it affected the greenhouse inner light and temperature to a great extent. Under the indoor steady state, the thermal properties of new type polyethylene terephthalate (PETP) film and several kinds of common covering materials were measured by the method of one-dimensional hot box. After analyzing the thermal transmittance of different materials, the following conclusion was drawn that the heat preservation property of PETP film was between those of 8 mm thick hollow PC board and 0.15 mm thick PVC film. Moreover, the heat preservation property of PETP film enhances with the increase of the thickness. Simultaneously, the FTIR spectrum of PETP film was also measured. After comparing the spectrum of PETP, PE and PVC film, it was found that in the range of 5～25 μm(the range of the earth surface thermal radiation), the transmittance of PETP was much less than those of the PE and PVC film. The results proved the superiority of heat preservation property of the PETP film.