The research of soil classification and soil grade evaluation is often based on fuzzy theory. So the traditional method has an inevitable problem about weight matrix which given by some experts. The finally result can be influenced by artificial factor. A new technique of falling dimension named projection pursuit is applied to soil study through using the improved real coding based accelerating genetic algorithm to optimize the projection direction. Thus, it can transfer multi dimension data into one dimension data, through searching for the optimum projection direction to realize the soil classification and its grade evaluation. The method can avoid the artificial disturb, and acquire preferably effect. Thus, it provides a new method to the research of soil classification and grade evaluation.