Global environmental degradation has been recognized as the most important challenge of the 21st century, and the development of green chemical methods to achieve environmental remediation is a common focus. As a typical representative of advanced oxidation technology, photocatalytic technology driven by solar energy has attracted attention due to its ability to activate oxygen molecules in the atmosphere into reactive oxygen species with oxidizing properties. At present, the development of photocatalysts has reached unprecedented prosperity, but people's understanding of the characteristics and analysis methods of molecular oxygen activation has always been insufficient, especially the lack of systematic summary and sorting. Herein, we focus on the properties and formation pathways of several typical reactive oxygen species (ROS), and summarize the latest advances for the detection of ROS in terms of both qualitative and quantitative detection needs, respectively. Then, preventative photocatalytic applications and performances of ROS, including applications in pollutant degradation, organic matter conversion and biological, are presented.