Although Kernel Principle Component Analysis(KPCA)has been used to monitoring nonlinear processes, it is not well suited for fault diagnosis. In order to solve this problem, a new method of fault detection and diagnosis for nonlinear processes based on KPCA and Least Squares Support Vector Machine(LSSVM) is proposed. The KPCA is used to monitor faults and extract feature and LSSVM model is used to diagnose fault, LSSVM model is constructed based on nonlinear principle component scores of various known faults. The applications in TE process illustrate the efficiency of the proposed approach.