A novel microring resonator sensor coated with a single negative metamaterial (SNM) layer is proposed. The dispersion relation of hollow cylindrical dielectric waveguide covered with a SNM layer is derived, and resonant frequencies of the corresponding whispering gallery mode are computed. We find that there is a good agreement between the theoretical results and numerical results of resonant frequencies and electric field distributions. Compared with traditional resonator sensor, the sensitivity and resolution are significantly enhanced by SNM, and the Q factor can be tailored by adjusting the distance between the waveguide and the microring.