By means of air oxidation electrochemical real-time monitoring, and X-ray diffraction (XRD), transmission electron microscope (TEM) and solution analysis, synthesis, oxidation and crystallization of hydroxycarbonate green rust GR1(CO₃²⁻) were investigated. At the synthesis stage when pH of the suspension drops to the lowest or the ratio of n(Fe² )/n(Fe_total) in mineral rises to the highest, GR1(CO₃²⁻) is formed completely. At the transformation stage when pH is controlld within the range of 6.5~10 at 25 ℃, with the rising pH, both the transformation rate and oxidation rate of GR1(CO₃²⁻) decreases, with its oxidate turning from lepidocrocite to goethite and magnetite, and the goethite crystallites increasing in size. When temperature of the suspension is controlled within the range of 15~45 ℃, with the rising reaction temperature, the transformation rate of GR1(CO₃²⁻) increases while oxidation rate decreases, with its oxidate turning from lepidocrocite to goethite and magnetite, and the goethite crystallizes increasing in size. When airflow is controlled in the range of 0 ~ 0.1 m³h^-1 at 25 ℃, with the increasing airflow rate, the oxidation rate increases, with its oxidate gradually turning from goethite to lepidocrocite and decreasing in crystallinity. Therefore, oxidation rate is a determining factor in the transformation of GR1(CO₃²⁻) under the influences of pH, temperature and airflow rate. With increasing oxidation rate, oxidate of the reaction turns from magnetite to goethite to lepidocrocite, and decreases in size of the crystallites and in crystallinity.