Abstract: Abstract: Based on the flowing characteristics of pulsating water injection in coal seam, the effect of water injection on porosity, water absorption and gas desorption was studied through the laboratory experiments. The results show that: (1) Under the action of pulsating water pressure, the effective influence range in the early stage and the reduction degree in the later stage of the fractures are both related to the hardness of the coal body itself. With the increase of the time for coal seam water injection, the growth rate of the effective influence range of water injection fracturing gradually decreases. (2) Coal seam pulsating water injection is beneficial to the development and expansion of coal fissures. However, it has little effect on the limit water injection of coal. The limit water injection of Sihe coal mine has only increased by 3.53%, one of Changping coal mine 2.76%. (3) After the water is injected into the coal seam, it is favorable for gas desorption in the early stage, but there is a water lock effect in the later stage. The gas desorption test of coal seam pulsatiing water injection in 4318 working face of Pingding coal mine also proves this conclusion. Therefore, according to the actual situation of coal mine, the water injection time is determined. The coal seam anti-burst can neglect the water lock effect. However, for gas mining, the measure of gas drainage is given priority should be taken.