The invention discloses a local mean mode decomposition-based stay cable time-varying cable force identification method. The method includes the following steps that: the vibration acceleration time-history data of a stay cable are acquired, and a signal processing method is adopted to perform signal denoising; Fast Fourier Transform (FFT) is adopted to estimate the fundamental frequency of the stay cable, and a bandpass filter is designed according to the fundamental frequency so as to primarily process vibration signals; a local mean mode decomposition method is adopted to decompose the processed vibration signals, so that the vibration modes of each order of the stay cable are obtained; and Hilbert-Huang transform (HHT) is adopted to process the signals, so that the instantaneous frequency time-history data of the vibration modes of each order are obtained, and a cable force-fundamental frequency formula is utilized, so that instantaneous cable force time-history data can be obtained. With the local mean mode decomposition-based stay cable time-varying cable force identification method of the invention adopted, the time-varying cable force of the stay cable can be obtained, anda defect that an existing cable force measurement method can only measure an average cable force can be eliminated. The method has the advantage of high measurement precision, low cost and wider application range.