Abstract: In order to reduce the energy consumption of the pressure swing adsorption (PSA) nitrogen making machine in the cryogenic liquefaction device of low-concentration coal-bed methane and increase the nitrogen yield of the unit compressed air, the technological process of the commonly used PSA nitrogen making machine was improved. To aim at the residual pressure of the exhaust gas in the process of nitrogen making, the exhaust gas recovery tank was added to collect and store the exhaust gas produced in the process of nitrogen making, the exhaust gas in this tank was then delivered into the drying tower, the front end of the drying tower was back-flushed by the exhaust gas instead of the the dry air to achieve the drying tower regeneration, and the dry air was all used as the feed gas for nitrogen making. After the improvement of the nitrogen making process, the full use of the residual pressure of the exhaust gas was made, and more nitrogen could be produced in the case of the same air intake, this thus achieved the purpose of energy saving.