In order to reduce the testing risk of an on-board embedded software and improve software developing efficiency, an on-board embedded software test planning method was proposed to plan the whole test process based on a butterfly model. Firstly, the principle of butterfly model was introduced. According to the characteristics of on-board embedded software, the on-board embedded software test planning method was put forward on the basis of the butterfly model test principle, and the advantages of the method were analyzed. Then, by taking an on-board camera embedded software for example, the software development process was planned with this method. Finally, the test results were analyzed. The results indicate that this method could discover and avoid requirement and defect errors about 80 percent and design and defect errors about 60 percent.Therefore, it can reduce software testing risk, shorten software development cycles, and improve the reliability of on-board em-bedded software.