The regression equation,y=-1.846 7+0.337x1+1.970 5x2-0.568x3+0.629 2x4,for calculating the leaf area and relative indexes of Trifolium repens was established by using its leaf length and leaf width as measuring indexes.The results showed that there was a very significant linear correlation between the regression equation and measuring indexes and its correlation coefficient was up to 0.987 3.The mathematical model with the simple and practical advantage can be easily used in measuring leaf area of Trifolium repens.