During the COVID-19 epidemic, hypochlorous acid (HClO) was frequently utilized for indoor and outdoor disinfection. The sensitive and selective detection of HClO puts forward high requirements for food safety. Furthermore, HClO is crucial for physiological and pathological activities. However, excessive HClO is harmful to the environment, animals, and humans. Therefore, it is imperative to construct a highly selective and sensitive HClO detection method to determine the safety of food and water, as well as the role of physiological and pathological processes. Herein, we successfully developed a near-infrared (NIR) ratiometric fluorescent probe FLD, which had high practicality and wide application range and was utilized to detect HClO in real samples and organisms. Probe FLD had the advantages of simple synthesis, high selectivity and sensitivity, significant colorimetric change, and low detection limit. Probe FLD was loaded onto test strips to create a single, reasonably priced solid sensor that enabled the visual detection of HClO. The experiments with real samples showed that the probe had good accuracy and precision. Importantly, the measurement of HClO levels in oxidative stress and ferroptosis models was successfully accomplished. Overall, probe FLD’s outstanding qualities make it a good prospect for application in environmental monitoring, food safety, and biology.