Based on plentiful geologic investigation data of the engineered slope at the Lancangjiang bridge, statistical analyses are undertaken to examine the structural planes with fitting test by the way of Chi-Square and Kolmogorov-Smirnov method. The results show that: 1) three preferred structure planes are in the right bank; 2) four preferred structure planes are in the left bank; and 3) the occurrence of those preferred structure planes are confirming with normal distributions, respectively. Statistic models of the engineered slopes are constructed to analyze the failure modes based on the statistic results. The failure model of the right bank engineered slope is sliding and fracturing; and the failure model of the right bank slope is the local rock blocks losing stability.