Abstract: On laboratory conditions,background leakage caused by temperature was one of the important factors influence calibration of pressure leak consequently,the constant temperature water bath of the calibration apparatus has been used,the method of initiative and passiveness were combined to keep constant temperature,to decrease the background leakage caused by temperature,through the research on experimentation,background leakage was decreased to the grade of 1.36×10^-9Pa×m³/s when constant temperature been used,the measurement’s lower limiting of pressure leak extended to 2.667×10^-8Pa×m³/s.