The sections of 14 loess natural slopes were measured along the northern edge of Bailuyuan, Xi’an, and then the geologic models were built. The parameters of physical mechanics of loess strata in different periods were obtained by in-suit testing and collecting data. The results showed that the stability coefficients of 14 slopes calculated by Monte-Carlo Method and Duncan Method were 1.11~1.41 and 1.09~1.33, respectively, and the slopes were basically stable-stable. The reliable indicator of slopes calculated by the above methods were 0.56~1.79 and 0.39~1.60 and the failure probabilities of slopes were 3.4%~29.0% and 5.5%~34.8%, respectively. The failure probabilities of 75% slopes were more than 10%, and the failure Likelihoods were high.