Rainfall and soak will often lead to instability of unsaturated slopes. This is mainly because with increasing of water content in soil mass, the matrix suction will reduce substantially and even disappear at all. In order to study the relationship between matrix suction and stability of unsaturated slopes, a typical unsaturated laterite slope in Jincheng Rail is numerically analyzed in this article utilizing strength reduction FEM program and taking the effect of matrix suction into consideration. Five cases have been considered in the typical unsaturated laterite slope model with different matrix suction from 120kpa to 0kpa, and the corresponding safety factors are calculated. Research results show that the safety factor of the laterite slope reduces gradually along with the reduction of the matric suction. When the matric suction is lost, the safety factor is less than 1.0 and a local sliding surface is generated on the upper section of the laterite slope.