Abstract: Biomineralization possesses the capability to bind granular materials, which can be used in the applications of geotechnical engineering as an emerging green ground improvement technology. However, little information is available on the mechanics of biomineralization, especially on the process of biocementation. An optical platform is proposed to visualize the process of biomineralization based on microfluidics. A series of micro-scale investigations related to this process are performed to capture the spatial distribution of calcium carbonate crystals, precipitation patterns and quantitative crystal growth rate. The results show that the convection and diffusion of solvent have significant impacts on the distribution of calcium carbonate, which demonstrates a nonuniform spatiotemporal distribution. The extent of uneven distribution in time scale is reduced as the reaction goes on. However, the phenomenon of uneven distribution in spatial scale is maintained during the whole reaction period (0~2200 min). Two precipitation patterns in biocementation are found in this study, i.e., precipitation at pore and precipitation at sand contacts. The precipitation at pore shows no growth axis, while the precipitation at sand contacts shows growth axis with different growth rates. These investigations may provide new insights into the mechanisms of microbial induced carbonate precipitation and are beneficial for the optimized design of up-scale application.