Abstract: Gas content is a key parameter in shale gas reservoir evaluation and reserve calculation,and its accurate test is the basis for calculating geological reserves and determining the development plan.At present,the commonly used field-test method needs to estimate the lost gas content,which leads to the low reliability of the test data.In order to clarify the real gas-bearing capacity of Longmaxi Formation shale in Southern Sichuan Basin,China,for the first-time,the field gas content test of the marine shale gas in a pressure-holding coring well was carried out in China.The pressure-holding coring technology can keep the core in the original formation pressure state and minimize the loss of gas in shale.Considering the particularity of the pressure-holding process,the direct testing equipment for shale gas content was developed,and a complete testing process and method were established and the gas content of shale can be measured under pressure.The new method needs to test the desorption gas in the depressurization stage and the heating desorption gas in the normal pressure stage.The total gas content of shale can be obtained by adding the two parts of test results directly,and there is no need to estimate the gas loss in the coring process.The results show that the average total gas content of pressure-holding coring section is 3.77 m3/t,which is significantly higher than that of conventional coring section.In addition,the direct test method of gas and free gas content in shale was also established.It is found that the free gas content of Longmaxi Formation shale is greater than the adsorbed gas content,the average proportion of free gas is 64.48%,and the proportion of free gas at the bottom of Longmaxi Formation is about 75%.Compared with the total gas content of shale gas wells in the same layer of an adjacent well,it is considered that the current calculation method of lost gas obviously underestimates the gas content of shale,and it is necessary to further calibrate and establish a new calculation method of lost gas combined with the results of pressure-holding coring.It is suggested to increase the number of test wells of shale gas pressure-holding coring wells in the future to further clarify the real gas-bearing capacity and reservoir capacity of shale gas reservoir.Especially for the exploration of new areas such as deep shale gas and marine-continental transitional shale gas,the pressure maintaining coring test can be used as a priority.