Considering the requirement of monochromaticity and tunubility for resonator used in on-chip optical interconnect source, we design and make a tunable silicon reflection cavity mirror based on microring resonator, using complementary metal-oxide-semiconductor technology and silicon material-on insulating substrate. The performance of the reflection cavity is analyzed by the transfer-matrix method, and we find that the reflection cavity shows good properties in sharpness and extinction ratio. The experimental results show that the reflectivity of the reflection cavity can reach 90% at the wavelength of 1549 nm, the quality factor is 3×104, and the free spectral range (FSR) is 9.6 nm. By applying the thermo-optic modulation to the microring resonator, the wavelength tunability in FSR can be realized within the power range of 0-40.5 mW.