The principal dimensions of naval ships regression analysis via trained BP network by improved PSO is proposed in this paper. Firstly, learning factor is adjusted dynamically, and the improved PSO is implanted in the BP network. Then improved PSO-BP is imported when establishing the regression model of ships’ principal dimensions and comparing its results with the results of polynomial regression. The result shows that BP network trained by improved PSO has higher accuracy and fine character of subsection smooth. Therefore, the model has guidance effect of importance to ship’s top demonstration and preliminary design.