Due to its closed-loop structure, the silicon microring resonator can have a very high quality factor value and its output intensity is very sensitive to different wavelengths. These characters, plus the potential in CMOS compatible fabrication process, are making the silicon microring resonator a key building block of photonic integrated circuits for the applications of filtering, switching, modulation, and wavelength conversion. In parallel, the silicon microring resonator has also been proposed as a compact and highly sensitive optical sensor. In recent years, microring sensing related research and development has been growing consistently and rapidly for the purposes of environment monitoring, health diagnosis, and drug development. This article will firstly review the recent development in silicon microring sensors, which are mainly concentrated in two areas: to improve the sensitivity and to enhance selectivity. In order to have better understanding of this class of sensors, the basic structure of the microring sensors, its working principle, and its unique properties will be described. Then, our own works, in particular, the methods to improve dynamic range, sensitivity, and stability of the silicon microring sensors, will be presented. By studying the fundamental optical properties of the coupled microring resonators, novel silicon microring sensors with better and more reliable sensing performance are constructed. Finally, through studying the interactions between chemistry and optics, acceleration and optics, the specific applications in glucose sensing and seismic sensing are discussed.