Abstract: The evaluation index system, which might help evaluate the impact of road construction on forest environment was built with four dimensions of ecological environment, social environment, ambient noise and ambient air quality. A comprehensive Fuzzy mathematical evaluation model was framed based on Fuzzy mathematical theory and that was applied to evaluate the influence of the road building of "Baijixun-Yanwa" upstream section of the highway along the Lancang River in Yunnan Province upon the environment in the forest area. The results showed that the road construction had middle level impact on the local forest environment, which was basically in the same level as the regional environment. Some countermeasures were put forward according to the sensitive factors to protect the forest environment.