Abstract: The principal component analysis could simplify data structures in the precondition of minimizing loss of original data information. By means of the principal component analysis, the important theoretical basis could be provided for the grading management of soil. Based on the investigation of garlic ecosystem geochemistry in Qixian, the mineral elements in the soil and garlic quality were tested. The fifteen mineral nutrition elements and garlic quality were chosen as main indexes for value, and the principal component analysis was used to evaluate all kinds of soils in this area. The result of sorting out the rank of soil was in accordant with practices.