Abstract: The phosphate buffer (1/15mol/L，pH 7.7 ) can decrease the harmful action of sulphurous acid to the wheat and sorghum seedlings. The test proved that the phosphate buffer had protective function to sulphurous acid harm. After wheat and sorghum seedlings were treated with the phosphate buffer, the root activities , proline content and solubility sugar content of seedlings were increased. The protective effect of phosphate buffer to sorghum seedlings was bigger than to wheat seedlings; besides the protective effect of phosphate buffer was different along with different ways of dealing with. Spraying the leaves was more effective than watering roots with phosphate buffer.