Abstract: The acquired data of aero-engine are somewhat contaminated with noise or disturbances.Different methods of noise separation such as the spectrum analysis,filtering,wavelet decomposition,bi-spectrum and auto-correlation analysis were discussed.Besides,the types and characteristics of noise radiated from the engine were analyzed.The results show that the engine noise is additive weak-intensity continuous spectrum or compound spectrum and for some frequencies it is both continuous and linear.The noise contains not only internal complex white noise but also non-stationary variance intrusion colored noise.