The realistic needs of mountainous highway construction in China are explored and studied on risk problem, which is inevitably exist in the mountain highway construction, otherwise, safety risk assessment of mountainous highway slope has important theoretical and practical significance. Highway slope safety risk prediction and evaluation methods are established which based on geological hazard risk assessment methodology. Safety risk assessment for Taishangou tunnel entrance slope of Shiyan to Baihe highway is studied by risk evaluation method of geological hazard. Monte Carlo simulation is used to get the stability of the slope probability of failure under the conditions of normal operation and abnormal conditions. And the vulnerability for the part of slope within the affected areas is analyzed. Possible economic loss and population casualties are obtained through the risk calculation formula. The results show that: Taishangou tunnel entrance slope is less risk in the natural conditions under the conditions of the acceptable range class; but slope is higher risk in non-normal conditions, management measures must be taken to reduce risk and to strengthen monitoring, particularly to strengthen the monitoring of slope deformation in the construction process and adverse natural conditions. The result is provided guidance for slope protection and safe operation of Shiyan to Baihe highway.