Abstract: Formaldehyde (FA) is one of the simplest reactive carbonyl species (RCS). Aberrant accumulation of formaldehyde in patients implicates not only in diverse physiological processes but also in various pathological processes, including neurodegenerative diseases, diabetes, chronic liver and heart disorders. In addition, some RCS in the environment are pollutants that threaten human health. Consequently, the development of sensitive methods, which can selectively monitor RCS in live cells, tissues and organisms as well as in environmental samples, is highly demand so that their biological roles could be understood and their concentrations in environmental samples can be determined. Recently, fluorescence as a powerful tool has attracted great interest in the design of high-performance sensors for in vitro and in vivo tracking formaldehyde. This article briefly describes the classification of fluorescent reaction-based probes for formaldehyde that rely on the reactive carbonyl of formaldehyde and the recognition unit, NH₂ group, NHNH₂ group, Aza-Cope rearrangement reaction and the new type of regeneration fluorescent probes. In particular, the latest formaldehyde regeneration fluorescent probe is highlighted, which firstly captures the analyses, induces imide bond cleavage, and then releases the captured formaldehyde molecule with simultaneous off-on fluorescence response. This article summarizes the formaldehyde-based fluorescent probes from the aspects of design concept, recognition mechanism and application.