Abstract: In order to obtain the characteristics of acoustic emission (AE) of materials with different particle sizes,the laboratory experiments on the characteristics of AE of rock-like materials with four different particle sizes under three-point bending are carried out. Then the characteristics of AE and mechanical properties of specimens are analyzed. The results indicate that there are two stages in the rock-like materials under three-point bending. With the decrease of par-ticle size,the peak load and the cumulative number of acoustic emission events at peak load are increasing,and the maximum of r values (the ratio of cumulative hits and cumulative energy) are decreasing. It also shows that the smal-ler the particle size is,the more AE events are generated with relatively high energy,and the variation law of D value of ringing count is decreasing. At the same time,the relative load level at the lowest point is higher. The main rupture stage is the sustained low value stage following the increase and decrease of b value. Then the lowest D value is taken as the main rupture precursor.