Abstract: The object researched here is a high-filled loess slope with the height of 105meters located in Northern Shaanxi. In order to study the engineering properties of the filling material, a great deal of laboratory tests have been done. Based on the geological condition and practical situation of the loess slope, a proper calculation model was established to calculate reliable index and failure probability of the slope at different underground water level under normal weather and heavy rainfall. The results suggest that the high-filled loess slope is in the steady state. Using fuzzy synthesize estimate method in the original design and made by 3 optimize program to choose the best type of optimization model.