A hydrogen-fueled engine was developed. The idle speed control strategy of hydrogen-fueled engine was established via the theoretical analyses on the mechanism of backfire phenomena of idle speed state. Through a great deal of idle speed experiments, parameters (position of electronic throttle, spark advance angle, ignition dwell angle, and hydrogen injection timing) optimization and the causes of speed fluctuation and backfire were analyzed. The idle speed control stability of hydrogen-fueled engine was studied with increment PID arithmetic. Meantime, PID parameters (proportion coefficient, integral coefficient, differential coefficient and control period) were regulated to favorable values. The experimental results showed that the high stability of both high and low idle speeds was realized and the target of optimization was achieved. 