To investigate the effect of supercritical CO2 saturation on acoustic emission (AE) signal properties in hot dry rock failure process, AE tests were conducted on granite under uniaxial compression. The results revealed that the strength of granite was obviously decreased after supercritical CO2 saturation, and new frequency bands appeared in the high-frequency region of AE and dominant frequency dispersion was enhanced. Dominant frequency mode was evolved from single mode dominated by high frequency to complex mode distributed in multiple frequencies indicating the failure modes diversified. Furthermore, supercritical CO2 saturation resulted in more uniform distribution of energy events and wider distribution of magnitude during granite failure. The decrease of b value as the prediction basis for failure might not be applicable. In addition, the degradation of the cementation degree of granite mineral particles and particle size were considered to be the fundamental reasons for the variation of AE properties. (C) 2020 Elsevier B.V. All rights reserved.