In this paper, the effect and mechanism of microbial induced carbonate precipitation (MICP) combined with carbon fiber for curing calcareous sand were investigated. The effect of carbon fiber on the effect of MICP on the consolidation of calcareous sand was investigated by a low-round grouting test, and the optimal amount and length of carbon fiber was determined. Subsequently, high-round grouting tests were carried out to study the sand column strength when MICP consolidation fluid could no longer be injected. Through comparative analysis of experimental results and scanning electron microscopy (SEM), the interactions among microorganisms, carbon fibers, and calcareous sand were analyzed. The test results show that the addition of carbon fiber can significantly improve the strength of microbial reinforced calcareous sand. In the low-round grouting test, the addition of carbon fiber can effectively improve the calcium carbonate production and specimen strength, and the calcium carbonate production in the fiber group increase by 15%-34% and the specimen strength increase by 135%-217% compared with the control group without fiber. In high-cycle grouting tests, when MICP consolidation fluid could no longer be injected into the sand column, due to differences in the number of grouting cycles between the two groups, the final calcium carbonate generation of the fiber group decrease by 4% compared to the control group without fiber, while the specimen strength increase by 11%.