The traffic accidents often occur in expressway tunnels in China nowadays. As a result, the characteristics and rules of traffic accidents in expressway tunnel are studied by collecting traffic accidents in expressway tunnels and analyzing the temporospatial distribution rules, types, vehicle types and causes. The results show that: 1) The highincidence time sections of single day are 9:00 to 10:00, 11:00 to 12:00 and 13:00 to 15:00. The proportion of traffic accidents occurred on weekends is about 40%. Traffic accidents occurred in January, February, April, May and July are more than those in other months. 2) The traffic accident modes in expressway tunnel are mainly vehicle rearend and collision. 3) The main causes of traffic accident are overspeed of vehicle and weather. 4) The vehicles, prefer to cause traffic accident, are cars with light chassis and heavy trucks.