In order to investigate the siltation mechanism of intercepting well with pressure, CFD was applied for numerical simulation, which was validated with field measurement data of sonar. On the basis of critical BSS model based on DPM, the probability selection method of GA was applied from a new point of view to put forward "probability sedimentation" model of particle. This model worked effectively on the simulation of silt surface and relatively siltation depth, which was validated with field measurement data of sonar. The results have shown that the silt surface of x-direction is a slope and there is a bulge with a location insensitive to flow. The silt surface of y-direction is concave and the middle surface swells while both sides tend to be flat because of scouring. The field measurement of sonar has shown that the silt depth in intercepting well is strongly relative to dry weather flow while the siltation condition of main intercepting pipe is relative to intercepting well.