Abstract: Microbial grouting reinforcement to repair the deterioration of masonry structures involves injecting microorganisms and nutrient solution ( a cementation solution) into existing granular system pores to induce the generated calcium carbonate cementation to form a microbial mortar of certain strength． Microbial grouting reinforcement is used when traditional grouting materials，such as lime，cement and epoxy，cannot be employed． The effects of the main factors on the strength formation of microbial mortar were systematically studied through the simplified laboratory and in-situ models． Thus，the methods for strengthening all sorts of deteriorated masonries by high-strength microbial mortar could be optimized，which would provide a basis for the using of microbial grouting technique in high-quality reinforcement of historical masonry buildings．