Underwater mass spectrometry is an important means for in-situ detection of dissolved gas in water．Its quantitative calibration depends on the preparation of different concentrations of dissolved gas，which takes a lot of time．Based on the different physical transport mechanisms，the process of dissolved gas passing through the membrane，pipeline transmission，and analyzer detection was decomposed and analyzed in this paper，then a rapid quantitative method that separates the process of sample passing through the membrane from the mass spectrometry detection process was proposed，and finally an experimental verification was conducted．The results showed that the permeation rate was highly linear with the partial pressure of the sample，with a correlation coefficient（,r,） of 0.998．Meanwhile，the membrane permeation efficiency could be determined by using a single set of data，and the relative error with the fitting results of multiple sets of data is 3.9%．Furthermore，the pipeline has a significant impact on the permeation rate．The traditional model that does not consider the pressure behind the membrane has a large error，but the pipeline transmission model that considers the pressure behind the membrane could reduce the error by at least 85.4%．The peak heights of the characteristic peaks in the mass spectrum are highly linear with the sample flux，and their correlation coefficients are all greater than 0.999．Based on the above conclusions，the step-by-step quantitative method was verified by using the bubbling method to prepare different concentrations of dissolved gas，and the maximum relative error between the calibration results and the gas chromatograph detection results is 10.9%．Therefore，a new method for rapid calibration of underwater mass spectrometers under time-limited conditions is provided.