Based on the moment tensor theory, a mesoscopic simulation method was proposed for acoustic emissions (AE) during Brazilian test in mesoscale. Its rationality was proved by comparative analysis between experimental and calculative results. This method can simultaneously provide the occurrence characteristics of AE events such as time, location and magnitude, and reproduce the spatial evolution law of fracture. It is found that before the peak tensile strength, the ratio and magnitude of AE events are lower, but from the peak tensile strength to residual tensile strength, the ratio and magnitude of AE events are higher. The ratio of AE events shows an extreme distribution with the variation of magnitude. Between the mean and peak value of magnitude, the cumulative ratio of AE events increases in an exponential function with the decrease of magnitude. The number of microcracks in each single AE event similarly increases in an exponential function with the increase of magnitude, but the ratio of AE events exhibits a negative exponential function relationship with the number of microcracks.