Floor confined water outburst is the main geological disaster in North China coal mining,  activation of fault and conduction of aquifer is the core cause of floor water outburst. In order to reveal the damage evolution of floor faults and the development law of water-conducting channels under mining disturbance, this paper took No.4108 Face of Longquan Coal Mine as the engineering background, and built a fully surrounded array microseism monitoring system to carry out three-dimensional dynamic real-time monitoring. Based on the elastic-plastic critical water outburst theory, the fitting discriminant model of floor failure depth and microseism release energy was derived. The 2D-CE confidence ellipse method was introduced to standardize the plane distribution of microseism events, and the fracture extension direction and water outburst risk level were determined by the ellipse inclination angle and area parameters. Combined with the temporal and spatial density of microseism events and the evolution characteristics of source energy, the danger zones of fault activation were divided. The field monitoring results showed that the microseism activity was weak when the fault was not disturbed by mining. When the working face entered the fault 100 m, it entered the stress concentration stage, and the microseism frequency and energy were significantly uplifted. When the dip angle of the long axis of the confidence ellipse approaches 90 °, the vertical fractures developed, and the risk of water outburst increased sharply. The set of microseism monitoring and analysis system could realize the advanced identification of fault activation and the dynamic forewarning of floor water outburst, and provide theoretical basis and field technical scheme for the prevention and control of fault water disaster in mining under pressure.