For satisfying the higher and higher application requirement to DDU for new type locomotives, a new modular designmethod of locomotive DDU’s application software was proposed. The software structure design was introduced, which realized thedisrelation between program and communication protocol and flexibility of locomotive primary attributes’ diversification configuration, aswell as adopted several mature logic processing modules to improve software developing efficiency and reduce the developing and testingcircle. The technology has been successfully applied in locomotive projects in Malaysia and Ethiopia, and achieved good results.