Abstract: Water inrush is the biggest safety risk during subsea tunnel construction stage,which often occurs in unfavorable geological bodies indicated by research.In order to understand and control the construction water inrush risk of unfavorable geological bodies in subsea tunnel,the type,factor and mode of water inrush in subsea tunnel are analyzed,the mechanism of construction water inrush of unfavorable geological bodies in subsea tunnel is analyzed,and failure of rock around tunnel induced by deformation is considered as the most reason,so it's very important to study the rock covers of no damaged,then the water inrush coefficient of water-resisting key strata is introduced and used as the criteria of water inrush judgment in subsea tunnel.In the case of F1 weathered slot in the left line of Xiamen Subsea Tunnel,the influence factors of water inrush coefficient are discussed,and some useful conclusions are given.At last,water inrush coefficient is applied in the prediction of water inrush in F4 weathered slot,and be proved feasible and applicable.