Iodine in the atmosphere directly influences on many kinds of photochemical reactions in troposphere, and indirectly poses impact on global climate change. It is thus that the research on the mechanism of atmospheric chemistry of iodine has attracted more and more attention. Iodine compounds in the aerosol are the final product of atmospheric chemistry reactions of iodine, which can be inferred and known via investigating the iodine speciation in aerosol. IO3- is often considered to be the dominant form of iodine precipitation. But field measurement in recent years showed that soluble organic iodine or I- were mostly the dominant forms in atmospheric aerosol. This implies that atmospheric chemistry mechanism of iodine still remain to perfect further. Here we focus on the research progress of atmospheric chemistry of iodine and its speciation in aerosols up to date.