Nitro-polycyclic aromatic hydrocarbons (NPAHs) are a class of trace organic pollutants with direct mutagenicity and carcinogenic activity. Therefore, this paper reviewed the origin, structure and nature of NPAHs in the environment. At the same time, the photolysis behaviors of NPAHs in simulated organic aerosol and the surface of solid particles and the NPAHs in solution were also discussed. The environmental significance of NPAHs was also indicated.