In this paper electronic control unit (ECU) used in vehicle-used compressed natural gas engine is developed independently. A series of start experiments are done with refitted JL465Q5 engine. Experimental monitoring system is developed as an interface connecting staff and single chip. Speed acquisition system is developed to record start process accurately in real time. The test results indicate that, more concentrated mixture is necessary when start speed is lower. Higher engine coolant temperature is conductive to cold start for natural gas engine. Multiple ignition control and ignition energy improvement is conductive to start successfully for natural gas engine. The results showed that electronic control unit (ECU) and speed acquisition system developed independently is practical and feasible.