Abstract: Urban rail transit lines launched at early phases in some major cities in China are seeing drastic growth of passenger flow. Passenger flow demand has far exceeded the originally designed line transport capacity. To improve the transport capacity and to ease operational pressure is imminent. Taking Xi′an Metro Line 2 as an example, the capacity expansion scheme of increasing train frequency and compressing operation interval is proposed, and a systematic study of the main factors controlling train transport capacity, including return capacity, scale of depot, power supply capacity, setting of the interval wind well, is carried out. The scheme examination calculation results show that when train frequency is 33 pairs/h, the reconstruction volume and investment are lower, while transport capacity can improve by 10%, equipped with certain level of anti-risk ability.