Abstract: There are many factors in land grading.It is very significative to determine the weights of factors.The traditional methods include the subjective and objective judgment.This paper proposes a genetic algorithm at the basic of concluding the research achievement of our predecessors.It over comes limiting factor of other methods,finds relationships and sequence of weighted by optimizing to fit the data sets based on setting up different targets.Genetic algorithm can dig up optimum weight sets of one field and find trends of one factor with the change of land-value in order to gain the classification of grading factors.This paper presents implementation steps of the method,verifies the feasible and scientific significance by examples,and achieves good results.