Abstract: The level of soil fertility of different aged(5-, 10-, and 20-year-old) Larix principis-rupprechtii plantation was assessed by using the method of principal component analysis, Norm value and membership function of fuzzy mathematic. The study found that the minimum data set of soil assessment comprises organic carbon, total nitrogen, nitrate nitrogen, ammonium nitrogen, available phosphorus, available potassium, acid phosphatase, urease and invertase.The value of available phosphorus was the smallest, the number was 014, and the ammonium nitrogen and urease took the second place, the number was 026. On the contrary, the membership value of available potassium and sucrose were maximal, reach to 075 and 074, respectively; In different aged Larix principis-rupprechtii plantation, the value of soil comprehensive quality index fall in between 043 and 057. Soil fertility showed a declining trend with age, the sequence is 5a＞10a＞20a; The consumption rate of phosphorus was more quickly than that of nitrogen, the rate was 994% and 111% respectively, so the restriction of phosphorus on the growth of Larix principisrupprechtii will increasingly prominent.