Considering the insertion loss of coupler， we theoretically analyzed the CRIT effect of the ring-in-ring structure resonator. In the process of the theoretical analysis， the transmission coefficient and effective phase shift were deduced using iterative approach， and then the dispersion was obtained， including the effect of the insertion loss. The analysis shows the effective phase shift， group velocity and bandwidth of the whole system can be controlled by the insertion loss， the multiples between the lengths of rings and the number of rings. The control of dispersion in ring-in-ring structure is important for applications of this structure in rotating sensor， optical delay line， optical buffer and filtering.