Reactive halogen species (RHS) is involved with many chemical processes in the atmospheric troposphere. It affects the sources and sinks of many important species in the atmosphere, and plays a significant role in the tropospheric chemistry. RHS chemistry in the troposphere is recently an important frontier research field in the international atmospheric chemistry research. The main field measure techniques of RHS in the troposphere include chemical amplification , atmospheric pressure ionization mass spectrometry (APIMS), differential optical absorption spectroscopy (DOAS) , mist chamber and wet chemical detection, photolysable halogen detector (PHD) and the isotopic ratios. Various observation methods show that different kinds of RHS exist in the atmospheric boundary layer, particularly in the marine boundary layer, polar boundary layer, and over the regions of salt lake. RHS concentrations vary from 10¹² to 10¹⁰. RHS can cause oxidation of some VOCs, influence the reaction of HOx and NOx, and make the loss of O₃. RHS impacts on the oxidation of sulfur and on mercury chemistry. The source of RHS in the troposphere is mainly from the emission of organic halogen and from the release of sea-salt aerosols. The cycle and transformation of RHS in the troposphere are summarized. Main scientific problems are put forward，and research prospect is made.