Abstract: Because the weak modes of structures are easily drowned in noise and hardly identified, a weak mode identification method is proposed upon repeated variational modal extraction of high energy modes. The autoregressive power spectrum is proposed to select the initial center frequency of the high-energy mode accurately. The high-energy modal component is decomposed by variational modal extraction method. After removing the high-energy component, the residual substitutes the original response for the initial center frequency selection and extraction of the next high-energy component. Mode shape identification is realized upon principal component analysis. A 10-degree-of-freedom numerical example under seismic excitation is presented to verify the effectiveness of the proposed method for weak modal identification under non-stationary excitation. The test data of the benchmark structure proposed by IASC-ASCE health monitoring group is analyzed to verify the effectiveness of the method in practical application. The results show that the proposed method can be used for weak modal identification of structures with noise under earthquake excitations.