The reinforcement process was directly completed on the ring shear apparatus by remolding the shear box to reveal the strength characteristics of calcareous sandy samples during microbial treatment.The influence of treatment time on the curing effect was studied using ring shear tests. The effect of vertical stress was investigated. The results of treated samples were compared with those without treatment of calcareous sandy samples. The results showed that the treated samples with shorter treated time and relatively lower strength can be obtained utilizing completing the curing process on the modified ring shear apparatus directly. The shear strength of the treated samples increased and reached a constant with increase of treatment time. The shear strength and residual strength of the sample treated 48 hours could reach 1.8 times and 1.6 times of the values for untreated samples, respectively. Compared with the untreated sample, the treated sample shows obvious strain-softening behavior, which may be related to the destruction of the cemented structure of calcium carbonate. Under the condition of high vertical stress (75~125 kPa), both the treated and the untreated samples show an obvious strain-softening phenomenon, but the reasons behind this phenomenon are different.