In response to the problem of water inrush from the floor of a roadway under the combined action of static and dynamic loads, a numerical simulation software FLAC^3D was used to construct a model based on engineering examples. From the perspective of the coupling effect of stress field, displacement field, and failure zone, the formation process and mechanism of water inrush channels from the floor under the combined action of dynamic and static loads were analyzed, and the degree to which key disaster causing factors affect water inrush from the floor of the roadway was explored. The research results indicate that the superposition of static and dynamic stress fields leads to an increase in the concentration and range of bottom plate stress in the depth direction. The dynamic load effect will increase the damage range and depth of the tunnel floor, reduce the thickness of the effective waterproof layer, and thus increase the risk of water inrush from the floor. The formation of water inrush channels on the roadway floor is mainly related to the amplitude of dynamic load, duration, and pressurized water pressure. Among them, the amplitude of dynamic load has a greater impact on the degree of water inrush. When the amplitude of dynamic load exceeds the critical value, the depth of damage to the roadway floor significantly increases. The increase in duration weakens the time characteristics of dynamic load action and is closer to static load action, reducing the possibility of tensile failure of the tunnel floor. The increase of pressurized water pressure reduces the effective stress acting on the rock layer under the roadway floor, reduces the strength of the rock mass, and increases the depth of floor failure. By using the single factor analysis method, it was found that the degree of influence of each disaster causing factor on water inrush from the bottom plate is in the following order: dynamic load amplitude > dynamic load duration > pressurized water pressure.