Abstract: In the direct method of determining coal bed gas content,how to reduce or accurately calculate the gas lost quantity becomes an urgent problem.From the view of shortening the coal samples exposure time in sampling process,a new inversion seal sampling device is presented in this paper,and the tests are carried out in NO.24 drilling field of 715 floor gateway in Qinan coal mine.Results show that the device can fetch clastic coal sample,and the coal sample is sealed when the sampling is completed.The fetched coal sample does not need to transfer,and the underground gas desorption is directly done by using quick-connect device of the sample silo.Compared with traditional core barrel sampling,the new device can significantly shorten the exposure time of coal sample in sampling process,the gas desorption quantity increases obviously in 30 min,which reduces the gas lost quantity and improves the determining accuracy of direct method in coal seam gas content.