Abstract: This paper reports the study of invertase activity in seed lings of Chinese fir(Cunninghamia lanceolata).Results obtained from several determinations indicated that the enzyme activity was the highest during pH 5.0 and Michaelis constant was 9.3×10-2mol.When the enzyme extracts were stored at 4℃ for 24 h,invertase activity in leaves and shoots decreased by 55.6 and 86.3 percent,respectively.There were differences of invertase activity among the leaf at the top,young leaf and mature leaf.The enzyme was most active in the leaves at the top of the seedlings and the enzyme activity in mature leaves was the lowest.They were 11.50,3.11 and 1.57 sucrose hydrazed μmol/h·g of fresh weight respectively.But invertase activity in young branchlet was five times as high as that in young leaves on the branchlet.Higher invertase activity was found in the fast growing clone seedlings than that in the slow growing clone seedlings.Correlation between invertase activity and seedling growth rate,and the possibility of determinating seedling growth potential by level of invertase activity were discussed.