Abstract: The stability of the excavation face in shield tunnelling is governed by factors such as tunnel diameter, buried depth and height of the water head; a sensitivity analysis was conducted regarding these factors using the finite element calculation software Plaxis8.2. The results show that: 1) the more sensitive factors such as internal friction angle φ, water head heights Hw, buried depth H and tunnel diameter D should be considered as the main reference factors for setting slurry pressure; 2) those factors caused by groundwater, such as seepage force and excess pore water pressure, will change the force condition of the excavation face, so the effects of groundwater must be taken into account while calculating and selecting the support force; 3) a shallow buried depth greatly affects the stability of the excavation face, and with the increase of the buried depth the effect becomes weak; 4) the relationship between the tunnel diameter D and the minimum ultimate supporting pressure on the excavation face is linear.