With the development of new micromachining processes, the traditional tapered fiber has derived thousands of different microstructured fibers. Among them, S-type fiber taper has been rapidly developed due to its small size, light weight, anti-electromagnetic interference and flexibility to be directly embedded in the structured system. With the intensive study on S-type fiber tapers, fiber optic sensors based on various structures and functions of S-taper have been continuously proposed for measuring temperature, strain, refractive index, humidity and magnetic field, etc., which enriches the types of fiber optic sensors and has deepened people's understanding of the sensing mechanism. This paper comprehensively reviews the research progress of S-type fiber tapers, including sensing principle, preparation method, various sensing structure combinations and sensing applications, and prospects for its development.