Microbial curing (MICP) can significantly improve the mechanical properties of sand. However, the curing effect is affected by many factors. In this study,the consolidated drained triaxial shear tests and electron microscope scanning tests were carried out to investigate the curing effect and the related mechanism of MICP. On this basis,the effects of cementation concentration, relative density and the proportion of cementation liquid's composition on the shear characteristics of bio-cemented sand were studied. The results show that with the increase of cementation level, the strength and brittleness of bio-cemented sand samples are increased. The increase of the strength of the bio-cemented sand is mainly due to the increase of the cohesive strength provided by the calcium carbonate crystal. The strength of the bio-cemented sand consists of the strength of the soil skeleton and the cementation strength of calcium carbonate.The former is influenced by the properties of sand and related parameters, while the latter mainly depends on the content of calcium carbonate crystals. The strength of the bio-cemented sand sample can be improved by using appropriate initial relative density of sand, increasing the concentration and the molar concentration ratio of urea in the cementation liquid.