With the gradual extension of coal mining to the deep, the risk of floor water disaster in deep high stress, high water pressure and high water temperature environment increased significantly, and the limitations of traditional water disaster forewarning methods became increasingly prominent. Microseism monitoring technology, with its significant advantages such as real-time and wide coverage, ran through the whole period of monitoring before and during mining, providing a more effective technical channel for water disaster forewarning. It was of great significance to clarify the evolution law of microseism events under deep complex geological conditions for the prevention and control of water disaster in mining floor. Based on the engineering background of No.15249N Face in Jiulong Mine, this paper used theoretical analysis, microseism monitoring, analytic hierarchy process and other means to study the microseism evolution law of coal seam floor under deep complex geological conditions, and evaluated the risk of water outburst. The risk value was determined, which was divided into high, medium and low. The study provided reference for the risk assessment of floor water outburst in Jiulong Mine and provided guidance for the formulation of water prevention and control engineering measures in working face.