The unconfined compression test model of biocemented coral sand was established by discrete element software.The model simulates MICP cementation by generating tiny calcium carbonate particles on the surface and contact of the coral sand particles, considering the contact of coral sand-coral sand particles, coral sand-calcium carbonate particles and calcium carbonate-calcium carbonate particles. The microscopic characteristics of biocemented coral sand with different cementation degrees, such as particle displacement, micro-crack development, and micro-crack distribution, were analyzed, which better explained the macroscopic deformation and failure mechanism. Results show that in case of unconfined compression, large displacement and failure occur at both ends of the material, while displacement in the middle part is small. The micro-crack development during the sample loading process can be divided into three stages, namely the compaction stage, the crack propagation stage and the rapid growth stage.With increase of the degree of cementation, the failure of the sample change from large pieces to small pieces or scattered particles, and the ratio of the number of tensile and shear cracks decreases, the difference of the number of microcracks decreases in all directions, and the crack propagation is more uniform.The proposed model can better simulate the cementation of MICP, and lay foundation for full understanding of the macroscopic deformation and failure mechanism of biocemented coral sand.