Abstract: Because the main composition of by-product from flue gas desulphurization(BFGD) is CaSO₄, it can be used for improving sodic soils, at the same time the content of salt in the soil is increased because of exerting BFGD. A pot experiment was conducted to study the law of sunflower emerging, soil chemical properties and soil leachate properties under different BFGD levels and different leaching levels. There were eight treatments designed in this experiment, including four BFGD levels(0, 7.5, 15 and 22.5 t/hm²)and two leaching levels(750 and 1200 m³/hm²). Results indicated that the germination rate of sunflower was increased, Exchangeable Sodium Percentage(ESP), pH value and Total Dissolved Salts(TDS) were decreased by applying the by-product, but excessive application of BFGD also had an effect on germination and growth of sunflower, and leaching could improve efficiency. It was inferred that the best BFGD requirement was 13.65 t/hm² when ESP=63.5, and pH=9.15 according to the test result. The result of the 4th treatment (7.5 t/hm² BFGD and 1200 m³/hm² leaching water) was the best in this experiment, the germination rate of sunflower is up to 92.5%, ESP, pH and TDS had dropped to 15%, 7.7% and 15% from initial 63.5, 9.15 and 0.65%, respectively.