Abstract: The coal seam being the main aquifer is a special geological condition,causing many water disasters such as inrush.Taking Xiao Jihan coal mine as an example,the geologic origins are researched and prevention system for water disasters in mines is established,based on analyzing hydrogeological conditions and water bearing characteristics of coal seam.The studies indicate that:the geologic origins that make coal seam main aquifer are contributed by the roof and cracks which intend to be loose when encountering water respectively,high permeability of coal,development of coal fracture and abundant supply of water.According to the origins,comprehensive technology system of preventing water disaster is proposed,including drainage from the ground and underground,grouting and plugging during exposing the coal,pulling the top to release pressure and catchment and discharging in the sump during tunneling,drainage in advance and pressure controlling during mining.The studies have been applied in 11203 workface in Xiao Jihan coal mine and turned out to be well.