In this paper, a photon calculation method with variable coefficients is proposed to solve the first order photonic differential equation a micro-ring resonator on silicon substrate with. The ultrafine solution of the photonic differential equation with different coefficients is realized. Based on the coupled mode theory, the transfer function of micro-ring resonator is analyzed in time domain and frequency domain. The etching depth is designed to be 220mm, and the silica-based ridge waveguide is designed to be 500mm. The shape of the micro-ring resonator is track type, which is composed of two semi-circle sandwiches with two long straight waveguides. The radius of the semi-circle is 30μm, and the length of the straight waveguide is 60.75μm. The coefficients of a and b of the differential equation can be adjusted, and the adjustment range of a0 is 1.5007×1010~1.5562×1010 and b0 is 4.5343×109~5.6473×109. The simulation realizes the numerical solution process of the differential equation with different coefficient and the adjustment and electric control of temperature. And it is compared with the real differential equation curve after normalization, and the error is less than 0.02.