Abstract: There are not many research works and reports on the communication based train control (CBTC) system loaded by 1.4 MHz bandwidth and 3 MHz bandwidth in the industry. In order to study the service carrying capacity of LTE-M system of urban rail transit under small bandwidth, the LTE-M system based on LTE technology is designed and tested on the spot of Qingdao metro Line 2. The results show that under the requirements of packet loss rate and delay, this system can carry 3 and 6 CBTC services under 1.4 MHz bandwidth and 3MHz bandwidth respectively.