Abstract: The methods of the constant volume and the dynamic comparison of quantitative gas are used in the calibration apparatus of pressure leak to calibrate the pressure leak. The calibration range of the leak rate is from 100 to 5 × 10^-3 Pa·L/s and the uncertainty is less than 9. 10 % with the method of the constant volume; the range is from 1 × 10^-2 to 5 × 10^-5 Pa·L/s, and the uncertainty is less than 14. 20 % with the method of the dynamic comparison of qauantitative gas.