Abstract: To thoroughly improve sealing effect of boreholes for gas extraction and solve practical problems of gas extraction for boreholes with easy-failure sealing segment in soft coal mine with high content of gas, we first propose reinforcing dynamic sealing technique. Based on the basic principles of the technology, field test at 53105 working face of Tianli Coal Mine is done. Experimental results show that reinforcing dynamic sealing technique has more significant sealing effect than the traditional ways under the same cases, and concentration of the gas extracted from boreholes improves from 9.6% to 36.5%. After the implementation of the technology, concentration and effect of gas extraction at 13105 working face in Tianli coal mine is significantly improved. The technology provides a new technical measure for borehole sealing under the condition of high gas contents, and has remarkable economic and social benefits.