The modeling of microring resonator modulators with phase rings is presented. The phase ring effect and the bandwidth optimization are studied by using the proposed model. Results show that the phase ring can enhance the modulation effectively. It also causes modulation resonances which worsens the modulation performances. Resonators with double phase rings keep the coupling region symmetric and have good phase enhancement ability. The amplitude of the modulated signal can be increased substantially while the phase rings are optimized by setting the operating point at the resonance point.