Abstract: Optimizing and controlling ignition timing is one of the important technologies to improve the cold start performance of hydrogen internal combustion engine. The combustion and performance of a hydrogen engine during cold start were investigated at different spark timing conditions. An electronically controlled hydrogen port-injection system was added to a four-cylinder commercial gasoline SI engine, and a new electronic control unit (NECU) was developed to realize the control of the spark timing. During the experiment, the lubricant and coolant temperatures were roughly kept at (24±0.5)℃, and the spark timing was varied from 25° BTDC to 10° ATDC. Results show that when the excess air ratio is 0.7, the peak cylinder pressure of the first cycle and the successful start duration for hydrogen engine first increase and then decrease with the retarding of spark timing. At the spark timing of 15° BTDC, the hydrogen engine gains the fastest successful start and the highest first cycle cylinder pressure. Flame development period is first shortened and then prolonged and flame propagation period is prolonged gradually with the retard of spark timing. The average emissions of NO_x, HC and CO are reduced by 84.9%, 33.6% and 23.8%, respectively, in the first 6 seconds during the cold start process.