Abstract: In the paper,two dynamic comparison methods were introduced.The me thods can be used to calibrate the leak rate from 1×10 -4 to 1×10 -7 Pa·m 3/s with the lower pressure of leak being atmospheric pressure.In dynamic comparison method with reference leak,firstly,test gas through unknown leak or reference leak was accumulated for different times to increase about the same quantity in a vessel which was filled with atmosphere.Secondly the mixed gas was expanded.Thirdly the expanded gas was introduced to a dynamic flow system and the dynamic balance partial pressure of test gas was measured and compared.In dynamic comparison method with quantitative gas,the quantitative gas takes the place of the accumulated test gas through reference leak.