An　electronic　control　unit　(ECU)　developed　for　automotive　natural　gas　engines　was　used　in　the　modified　model　JL465Q5　gas　engine　to　investigate　its　starting　characteristics.　The　AVR　single-chip　processor　was　adopted　as　the　core　controller　and　the　ECU　was　of　multi-chip　structure.　The　starting　intake　air　flow　was　adjusted　using　an　air　bypass　valve　controlled　by　a　step　motor,　and　the　natural　gas　delivery　was　controlled　by　the　electronic　gas　injector.　An　experimental　monitoring　system　was　developed　as　the　interface　of　man-machine　interaction　and　a　speed　acquisition　system　was　designed　to　record　accurately　the　starting　process　in　real　time.　The　test　results　indicate　that　for　the　natural　gas　engine　rich　mixture　is　necessary　for　starting　at　low　speed;　higher　coolant　temperature　is　beneficial　to　engine　cold　starting;　multi-strike　ignition　and　high　energy　ignition　are　also　contributive　to　engine　starting　successfully.