Abstract: In the process of hydraulic enhancement measures in underground coal mine, the resistance loss caused by the small pipe diameter, large velocity and long transport distance of the pipe for liquid flow is very large, which leads to the lack of pressure at the operation point. In view of this problem, this paper compared and analyzed the thermal stability, resistance reduction, shear stability and other main performance parameters of four commonly used resistance reducing agent, including guanidine glue, UG-3, DR-12 and EM30, the DR-12 resistance reducing agent of emulsion polymer was the most suitable for hydraulic permeability increasing measure in underground coal mine. The variation characteristics of resistance reducing rate of DR-12 resistance reducing agent with pipe diameter and flow velocity under different mass fractions were studied, the optimal proportion and determination method of DR-12 resistance reducing agent under different working conditions were obtained. Field application results show that the pure gas rate of boreholes, which are disposed by hydraulic permeability increasing measure with DR-12 resistance reducing agent, is 5.3 times of the pure gas rate of the ordinary drilling borehole, and it increased by 19.1% compared with the pure gas rate of water slotted drilling borehole.