There have been many studies on microbial cemented sand; however, the meso-deformation characteristics and the fracture process of the materials are not clear. Using the discrete element method and introducing the theory of moment tensor, the mesoscopic model was constructed for microbial cemented sand during Brazilian test, and its acoustic emission characteristics were studied. It is found that with the gradual increase of strain, the fracture strength expands from the top and bottom of the sample along the central axis, the value of the fracture strength increases continuously and eventually forming the main axis along the sample axis. The acoustic emission (AE) frequency and burst strength are normally distributed, and the burst strength ranges from -7.52 to -5.79. The exponential correlation between the numbers of AE and the micro-ruptures is negative. This study provides a new way to find out the rupture process of microbial cemented sand.