Abstract: n this paper, the factors affecting the satety tickness of roof of shallow underground excavation in Chongqing City are analysied with referencing previous data. The mechanism for failure under the effct of interaction between the foundation and the undergraund excavation, the effect of every factors on the safety tickness of roof and the variability law are studied by means of FEM numerical simulation. The safety thickness of roof forecasting model is obtained by stepwise regression analysis.