Abstract: Reasonable value of geotechnical parameters has a significant influence on engineering design. In order to evaluate the influence of soil parameter uncertainty to tunnel face stability, Monte-Carlo random simulation is used to analyze the influence of the variability of soil parameters and sample capacity level to the tunnel face stability, the reasonable safety factor of soil tunnel face stability is determined. The rationality of the design safety factor is evaluated through engineering example. According to the results, the uncertainty of the soil parameters has little effect on the stability characteristics of the tunnel face when the sample capacity is large. If the sample capacity is small, the influence of variability of soil parameters increases when the sample capacity decrease. It provides a basis for the support design of the temporary tunnel face.