Acoustic emission tests of coal-rock specimens under uniaxial compression were carried out; then the long-range correlation and multifractal characteristics of acoustic emission strength sequence were analyzed by multifractal detrended fluctuation analysis method (MF-DFA). On this basis

the trend of long-range correlation exponent H of AE strength sequence with different stress levels was studied. The results show that the inner fluctuation of AE sequence is a well-regulated multifractals

which is rather a long-range correlated process determined by intrinsic self-similar properties and not complete random on time scale. The trend of AE parameter H corresponds well with the process of coal-rock fracture development; the ‘maximum-decrescence’ model of which can be used as a precursory factor of coal-rock failure. The results provide a theoretical basis and method for monitoring and forecasting coal-rock stable condition based on acoustic emission in site.