Abstract:The maximal Lyapunov exponent(MLE) can reveal the nonlinear chaos feature of the dynamical evolution of steep slopes,and the MLE derived from multivariate time series is more practical than univariate time series. The 3D multivariate phase space reconstruction is investigated. Then,the modified method of bi-direction search is developed for calculating the MLE from 3D deformation time series based on the reversible and irreversible properties of time trajectories. Finally,the proposed method is applied to the high slope No.2 at Xiaowan Hydropower Station. Bottom-up towing deformation mechanic of this slope is obtained by the MLE used as the judging criterion of slope stability zoning,which agree well with practical situation. Thus,the proposed method is proven to be effective and reliable,and the research results have useful references to the evaluation and prevention of stability zoning of high slopes.