Abstract: In recent years, there is a view that "the train with dynamic towing proportion of 66% is better than the train with dynamic towing proportion of 50%", which leads to the blind increase of train power in various regions. Some cities even invested 5M1T and 6M2T in the train lines, which caused the energy consumption of train traction and the operating cost to increase. Taking Chongqing metro line 5 as an example, the traction characteristics of 4M2T and 3M3T trains (type B) were studied by means of simulated traction calculation, and it is revealed that the traction energy consumption, braking force, regenerative braking force, traction capacity and climbing capacity of the train are not directly related to the number of bullet trains. It is suggested that each city should choose the vehicle grouping method and power allocation of trains reasonably according to its own characteristics, so as to reduce the investment and operation cost of subway construction projects.