In order to make a quantitative description for the running status of the scroll compressor, a fault diagnosis method of information entropy is proposed on the basis of the theory of entropy. This method is based on singular spectrum entropy in time domain, power spectrum entropy in frequency domain, wavelet power spectrum entropy and wavelet space feature spectrum entropy in time-frequency domain, which is used as the comprehensive appraisal index of quantitative feature for vibration status of scroll compressor. Under condition of invariable speed operation, the identification of natural frequency is carried out. Meanwhile, the influence of the axial vibration of moving scroll, radial compliance mechanism and slight liquid slugging on the scroll compressor is analyzed quantitatively. Three forms of periodic cataclysm of moving scroll under variable speed operation and the variation of information entropy with rotational speed are disclosed. Results provide basic data for the fault diagnosis of scroll compressor.