Redox state indicated by reactive oxygen species (ROS) level is a cellular physiological feature. Redox status is exactly controlled by  conserved system. Its alterations consequently modulate various biological activities and play important roles in cells and organism under physiological  and pathological conditions. Hence detection of redox state is deemed as an important technique both in basic and clinical researches. The present article  reviews the principle and current applications of fluorescent probes or sensors for redox detection. With comparison of properties of various probes,  especially genetic coding fluorescence probes, much understanding will be gained. And the review helps us to understand how to apply the redox probes  on the biological and clinical researches and eventually look forward to new applications in the cell and whole animal level.