A set of pot experiments was conducted to assess the effect of application of flue gas desulfurization gypsum (FGD-gypsum) with different rates of (0, 5, 10, 25 and 50g/kg) on chemical properties of saline-sodic soil in Shanghai tidal flats and plant growth. The results showed that soil salinity can be decreased by appropriate rates of FGD-gypsum addition, promoting plant growth. Compared with the blank treatment, at FGD-gypsum addition rate of 25g/kg, the soil pH and alkalization degree (ESP) were reduced by 5.45% and 61.5%,contents of soluble Cl^- and CO₃^2-+HCO₃-reduced by 33.0% and 22.7%, and soluble Ca²⁺ and SO₄^2- increased by 85.1% and 96.3% respectively at significantly level of P < 0.05. The treatment also found that the content of soil organic matter and available phosphorus were reduced by 17.5% and 54.0%, and available potassium increased by 39.5% respectively. Fruit fresh weight, root fresh weight and plant stem of tomato were increased up to 144%, 54.3% and 9.53%, and plant fresh weight and root fresh weight of ryegrass were increased up to 46.6% and 17.0% by increasing rates of FGD-gypsum addition, while the excessive application of FGD-gypsum (50g/kg) seriously harmed to plant growth. FGD-gypsum application rate of 25g/kg is recommended as the optimal and safe application rate of FGD-gypsum for saline-sodic soil amendment.