Abstract: In order to study the water inrush mechanism of working face cross-fault under high water pressure condition, on the basis of studying the distribution law of ground pressure and water pressure around working face, it theoretically discussed the deformation characters of the floor strata during the period of normal mining and cross-fault mining by establishing mechanical model, and finally obtained water inrush mechanics criterion of cross-fault mining during early mining period and weighting process. The research results showed the vulnerability area of water inrush was from the mining coal wall to the gangue compaction area of goaf; in the case of similar geological conditions, the volume of floor bending of mining across fault was 48 times of the volume of floor bending of normal mining, so water inrush was more likely to happen as mining across fault; because of the opposing forces, the possibility of water inrush reduced in the weighting process; in order to pass the fault safely, the distance from fault fracture zone to gangue compaction area should be less than the limit cantilever span of floor beams.