The effective control of water and mud inrush has become an important topic in the field of underground engineering disaster prevention and reduction. With the aim to better understand the mechanism of water and mud inrush in fault zone, the finite element calculation model for simulating the dynamic excavation of the tunnel crossing fault zone is established by taking water and mud inrush disaster in the fault fracture zone of Yonglian Tunnel on Jilian Expressway, Jiangxi for example. And then, the precursor information evolution process of the seepage field, stress field, plastic zone and tunnel water inflow during tunnel excavation is analyzed, being useful for revealing mechanism of water and mud inrush from faults. The results show that: (1) The stress concentration reaches the maximum, and the stress increases on average by a factor that is greater than 1; the high stress concentration easily leads to the instability of surrounding rock near the fault. (2) The crown settlement and arch uplift dramatically increase. (3) The seepage velocity increases sharply, the groundwater is more likely to infiltrate into the tunnel, and the erosion and failure of the surrounding rock increase. (4) The plastic zone covers the whole tunnel and the yield depth increases. (5) When tunnel face approaches to the fault, water and mud inrush is entirely possible to occur, which should be actively treated.