Abstract: There are numerous small or medium-sized mines in the eastern Hubei where instable accidents of mining excavations frequently happened.How to accurately and effectively analyze and predict the stability of mining-out area has been one of the important issues.Based on the application status of acoustic emission in the eastern Hubei，the AE differential ratio indicator was put forward，which took into consideration of such three AE parameters as the large acoustic emission events，and the total event period and the energy rate within a period of time.It can effectively reduce the interference on sound monitoring parameter fluctuations from the external environment，different geological conditions and different structures of the mined zone.Through comparing with the variation of the cumulative value of rock acoustic emission parameters in mined-out area，the general changing rule of the corresponding AE differential ratio indicator and its precursor characteristics of instability were obtained.The AE differential ratio indicator can not only reasonably and effectively analyze the stability of the mined-out area，but also simply and accurately predict the instable time.Then，AE differential ratio indicator was applied in Pumin iron mine in the eastern Hubei to predict the stability of mined-out area，and the prediction result was basically in accord with the actual situation，indicating that the indicator has certain applicability and rationality.

Key words: Differential ratio indicator, AE(acoustic emission), Mining-out area, Instability prediction