Microwave photonics is a field that studies the interaction between microwave and optical waves for the generation, transmission, processing, and measurements of microwave signals by means of photonics, to take advantage of the high speed and broad bandwidth offered by modern photonics. Microwave photonic sensors are one of the active sub-fields that uses microwave photonic techniques to achieve high-speed and high-resolution measurements. In this article, microwave photonic techniques for optical sensing demonstrated in the past few years will be reviewed including high-speed and high-resolution sensing based on heterodyne beating oftwo opticalwavelengths,the use of an optoelectronic oscillator to translate the optical wavelength shift to a microwave frequency change, and the use of wavelength-to-time mapping to translate the sensing information from the optical wavelength domain to the microwave frequency domain, to increase the interrogation speed and resolution. The use of photonic integrated circuits to achieve high-speed and high resolution microwave photonic sensing will also be discussed.