Optical microring resonator based on SOI (Silicon-on-Insulator) are w idely used in optical interconnects,optical communications and optical information transmissi on on account of low-power,high-integration and high-sensitivity characteristics.In this paper,a ring reflector with tunable reflectivity,bandwidth and wavelength is presented by us ing the coupling mode theory,the theory of microring resonance and thermos-optic effec t in the band near 1550nm.The radius of the ring resonator is 10μm．The channel waveguide structure is adopted.The width of the waveguide is 450nm.The relationship between the output spectrum and parameters such as the coupling coefficient k is discuss ed by simulation with the use of transfer matrix method and matlab.It shows that the reflectivity can be tuned from 15% t o 100% with no loss,and the range of the 3dB bandwidth can range from 0.25nm to 0.95nm.A FSR (free spectral range) variation of the wavelength can be reached by heating the electrode on th e microring resonator.The ring reflector as an important optical device of optical communic ation plays a key role in the aspects of gain spectrum equalization and channel selection.