Abstract: The characteristics of BP neural network and chaos optimal method are analyzed. By integrating chaos optimal method with gradient-decline method, an optimal method of combination search is created. Combining a large amount of piles testing data of the Pearl River Delta, the prediction model of vertical ultimate bearing capacity of single pile is established, based on chaos optimal method and BP algorithm. Real example research shows the predicted data agree well with the measured ones. It shows that the method is feasible, effective and satisfied with engineering demand, which can be used widely in projects.