Hydraulic conductivity of soil reduce significantly after MICP treatment, but it lacks theoretical calculation of the hydraulic conductivity of MICP-treated soil. The hydraulic conductivity of granite residual soil treatment by MICP were studied by theoretical derivation and experimental verification. According to the kinetic equation of enzymatic reaction, the expression of CaCO3 contents in MICP mixed soil was derived; furthermore, according to of MICP mechanism, the particle size and number of CaCO3 crystals are calculated by CaCO3 contents and the volume of bacterial. Void ratio, tortuosity and average specific surface area of grain are deduced and substituted into Kozeny-Carman equation, a theoretical expression of hydraulic conductivity of MICP-treated soils is proposed. The results show that the expression of CaCO3 contents presents a good capability to calculate CaCO3 contents of MICP treated granite residual soil. CaCO3 contents increases sharply at the beginning and then become stable. Concentration of the cementing solution in the range of 0.5~1.25 kmol/m3, higher the concentration of the cementing solution result in higher CaCO3 contents. The theoretical expression of hydraulic conductivity presents a good capability to describe measured predict hydraulic conductivity of MICP treated granite residual soil. Hydraulic conductivity of the specimens with the concentration of 0.50 kmol/m3, 0.75 kmol/m3, 1.00 kmol/m3 and 1.25 kmol/m3 of cementitious solution decreased by 35%, 40%, 45% and 55% respectively. Finally, examples also indicate our findings provided valuable insights into prediction of CaCO3 contents and hydraulic conductivity of MICP treated granite residual soil.