A method of contingency screening for filtering secure predefined contingencies is proposed.It can be used for online dynamic security assessment.The approach is based on the time domain simulation.Based on the theoretical derivation of the system linearization at the non-equilibrium point after disturbances，the sate matrix of the system and the coefficient eigenvalues can be calculated.The secure contingencies can be identified by analyzing the eigenvalues.Three simulations on different systems testify the validation of the proposed approach.