Microring resonator is a key component in integrated optics, and its filtering characteristics in application are affected by the input optical power. However, the steady model of microring resonator only includes the linear optical effects for a long time. In this paper, a new steady model of microring resonator is deduced. The loss and phase shift in the feedback waveguide of the microring resonator and the modification of coupling ratio in the microring coupler induced by optical nonlinear effects are taking into account, and following nonlinear optical effects in silicon waveguide are included: self-phase modulation, two photon absorption and thermal-optical effect. Then the influences of two photon absorption and the modification of coupling ratio in the coupler induced by the optical nonlinearity on the depth of notch filter are emphatically discussed. Simulation results show that when the thermal-optical effect and the self-phase modulation generate the frequency shift of the resonance spectrum, the change of the coupling ratio of the power dependent coupler has a great influence on the notch filter depth of the microring resonator.