Tests were done to research the influence of intake preheating during start process for electronic controlled diesel engine by using the electronic controlled diesel engine which was combined with VP37 electronic controlled distributor type injection pump management system and VS100 demarcate system. Tests were done to research the end symbol rotate speed of start，which influenced the performance of electronic control diesel engine during start process. Optimization process of fuel supply map during start process was drawn under the condition of intake preheating through the tests. The conclusion was also reached——the limit data of engine’s speed increased during the period between end of start phases and effective terminal of start fuel supply map was decided by the engine’s inherent characteristic. 