The heat removal effect of a long-term metro line in South China is studied. Through the test section of track tunnel, tunnel, the effect of condenser inlet air temperature of train, the exhaust fan heat removal effect is obtained, the results show that after closing the exhaust fan, the average temperature and daily maximum temperature of the station tunnel are both increased by 0.7℃, the average temperature of the interval tunnel measurement point is increased by 0.8℃, and the daily maximum temperature is increased by 0.9℃. The average air inlet temperature of the condenser at the train stop station in the evening peak is increased by 2.4℃, and the air inlet temperature of the condenser in some stations exceeds 45℃.Though the tunnel temperature still meet the specification requirements, (not exceeding 40℃), but have been unable to guarantee the normal operation of the train air conditioning during the afternoon rush. The opening of the fan has an obvious effect on restraining the temperature rise of the tunnel, especially in ensuring the normal operation of the train air conditioning condenser. The test results show that it is necessary to set up the exhaust system in South China, and provide a reference for the design optimization of the system.