Owing to their advantages of anti-electromagnetic interference, chemical resistance, high sensitivity, and fast response time, optical fiber sensors (OFSs) are widely used in biomedical, environmental monitoring, and food safety fields. We introduce the classification and principles of OFSs and summarize the applications and research progress of OFSs in water quality detection (heavy metals and microorganisms) and air quality monitoring (COx, NOx, and VOCs). Meanwhile, analytical performance, reliability, and environmental adaptability of OFSs are discussed and prospected.