Under the control of the tow-Yun fracture, the geological conditions are complicated and the rock strata is broken in Shiyan area ,in the northwest of Hubei province, and the rock mass is weathered into fragment. When Highway is built in this area, a lot of tunnel portal slope and landslide problems will be met. To properly solve these problems, it is needed to analyze the slope stability and to propose appropriate management measures. In the paper, taken a highway tunnel portal slope in Shiyan area for example, a detailed research was made on the mechanism of landslide formation, and using laboratory soil test results and the simple Janbu method, the local and global slope stability is calculated. The results show that the slope is stable in natural state, and in heavy rains the stability coefficient is reduced quickly and the slope will be sliding. So the slope needs to manage and the rain water needs to control.