Abstract: An new method of calibrating vacuum gauge which produce standard flow by using constant volume flowmeter is proposed in this paper.The constant volume flowmeter works in two modes: one is constant volume mode which can provide the flow of（10^-2～10^-8）Pa.m³/s,another is constant conductance mode which can provide the flow of（10^-6～10^-11）Pa.m³/s.By this way,the standard flow range is extended.Compared with the constant pressure flowmeter,constant volume flowmeter has the advantage of facility,simple structure etc.The measure range of vacuum calibrating device using constant volume method is 10^-2 Pa～10^-6 Pa,the evaluating of uncertainty is（0.67～1.74）%.In addition,an extraction gauge was calibrated by using two types of flowmeter,its distinction is under 5.7%.