As the heat releas of equipment in metro system has rarely been measured before, the cooling load of equipment stations is often overestimated in the design stage of air conditioning system, which causes the overlarge equipment selection, unit configuration and results in a great waste of energy and economy. In this study, the actual cooling load is analyzed based on onsite measurement in metro systems, including electric control room, communication equipment room, communication power room, signal equipment room, traction network room, traction transformer room, high voltage switch cabinet room, step-down transformer substation and other equipment rooms. The results show that the actual cooling load of high voltage switch cabinet is only 21.21% as design load, for communication equipment room and traction transformer room is 41.51% and 46.43%, respectively. The actual cooling load of all equipment rooms is only 42.33% as design load. The sensible heat ratio of equipment rooms in metro system ranged from 30% to 70% in general. Moreover, it was proved that the piston wind and unbalanced air volume can increase latent cooling load and decrease the sensible heat ratio.