The principle of the integrated cooling system on intercity EMUs was introduced, and how to calculate and select the main parts of the cooling system such as heat exchanger, water cooled heat sink, pump, fan and expansion tank was detailed. The design method of cooling system and the role of the core parts were especially introduced in detail. At last, the reasonability of the cooling system was proved by the results of the type test on the traction converter, so which could be used as a guidance for the integrated cooling system.