Reactive carbonyl species (RCS) are involved not only in diverse physiological pathways but also in various pathological processes, including Alzheimer's disease, diabetes, cardiovascular disease, and other malignant diseases. Therefore, it is essential to develop a simple and sensitive technology which can be employed to selectively monitor RCS in living biological samples, such as living cells, tissues, and animals. The subtle changes in the concentration of RCS in organisms can be detected by this technique. In this review, the design strategies of the typical examples of RCS fluorescent probes are highlighted and discussed. These advanced RCS probes may set the foundation for biomedical research on dynamic real-time monitoring of RCS in living systems.