Abstract: In this article,theoretical calculation formula for measuring the static evaporation rate by the pressure rise method is derived through theoretical analysis of the thermal properties of cryogenic medium in the process of natural boost heat transfer,and based on the first law of thermodynamics.By analyzing the influence of filling rate and effective volume on the natural boosting process and studying the measurement results of each time node of pressure rise method in 24 h,it can be found that the "T-P" curve is linear and approximately a positive proportion function.The higher the initial filling rate is,the slower the natural boosting rate is.When the filling rate is less than 80%,the difference of natural boost-ing rate increases gradually,whereas when the full rate is greater than or equal to 80%,the difference of the boosting rate is relatively small.Besides,the smaller the effective volume is,the faster the boosting rate is.When the testing time of boosting method is less than 6 h,the measurement error of static evaporation rate is larger than that of weighing method and flowmeter method,but the relative error decreases with the extension of testing time,while when the testing time is be-tween 6 h and 24 h,the error range of the measurement results of the pressure rise method is less than 3% compared with that of the weighing method and the flowmeter method.Therefore,the rationality of theoretical analysis and the accuracy of calculation formula are verified,and the testing time of the static evaporation rate can be reduced to 6 h,which provides a reference for the future revision of the standard.