The method and steps for software modeling of the embedded control systems for diesel engine based on UML are described in this paper. In order to meet the software function and the features of the system, object-oriented modeling for diesel engine embedded control software system has been implemented. Requirements are depicted by use case diagram and the logic structure is depicted by class diagram. According to the domain knowledge and the class diagram, the sequence diagram and state diagram are developed to describe the dynamic behavior of the system. The level of software development has been enhanced to the system level by software modeling. It focuses on the automotive field, and can be easy to grasp the problem from the overall perspective and discover software design problems at the early stage. It is also convenient to solve the problems caused by the change of requirements. The model has an excellent flexibility so that it can be applied to different software platforms. This method provides strong support to make the open architecture and reusability of the embedded software for diesel engine control come true.