Based on the idea of "treatment of waste by waste", the authors studied the reaction temperature, time span, liquid-solid ratio and nitrogen-sulfur ratio of carbon dioxide fixation by phosphogypsum carbonation, which affect the rate of conversion of phosphogypsum by wet carbonation treatment. The mineral phases and micro appearance in phosphogypsum and the product were analyzed by XRD and SEM-EDS. The results show that gypsum in phosphogypsum is wholly transformed into calcite, a little anhydrite is transformed into calcite because of its low solubility, and quartz is inert in the reaction. Under the optimum technological conditions, the conversion of phosphogypsum takes place under the conditions of temperature 65℃, time of reaction 60 min, liquid-solid ratio 3.0, and nitrogen-sulfur ratio 2.25, with the best value being 95.24%. The result is of some practical significance for conversion of phosphogypsum into fixed carbon and reducing discharge as well as further resource utilization of phosphogypsum.