As a novel environmentally friendly reinforcement method, the microbially induced carbonate precipitation (MICP) reinforcement technique has developed rapidly in recent years. The traditional MICP reinforcement method is limited by high reinforcement cost, poor environmental adaptability of exogenous mineralizing bacteria, and potential risks associated with the introduction of exogenous bacteria. The biostimulated MICP method using indigenous urease bacteria contained in soil can effectively reduce reinforcement cost and potential risks. In this paper, the biostimulated MICP method was used to reinforce the soil, and large-scale triaxial consolidation drained shear tests were carried out on specimens before and after treatment to compare and analyze the shear characteristics of the treated and untreated specimens. Moreover, the distribution and reinforcement mechanism of calcium carbonate in the biotreated soil specimen were also investigated. The results show that the biostimulated MICP treatment primarily generates rhombohedral-shaped calcium carbonate, which is deposited in the soil, leading to a significant increase in strength and stiffness, as well as a significant reduction in volumetric strain. The content of calcium carbonate in the soil specimen decreases with the increase of specimen depth, which leads to shear failure at the bottom of the specimen.