The Hilbert-Huang transform(HHT)was proposed to analyze the response signal of flange bolt joints structure under random excitation.The energy distribution law of every intrinsic mode function(IMF),the marginal spectrum and time-frequency spectrum of response signal under different preforce were obtained.It is shown that the percentage of IMF energy distribution has strong rule under different preforce, which can well reflect the loose condition of bolt joints structure; the HHT three dimensional time-frequency spectrum can intuitively show the situation of energy distribution with preload changes, and using adaptive HHT to analyze flange bolt joints structure under vibration environment is more suitable.