Combined cooling heating and power (CCHP) system can be efficient, economical and environmentally friendly, depending on the global optimization design of equipment selection, equipment capacity and operation strategy of CCHP system. This paper proposed a three-stage collaborative global optimization design method for CCHP system. On the first stage,discrete particle swarm optimization was applied to solve the optimal equipment type problem with maximum annual primary energy utilization rate. On the second stage, particle swarm optimization was utilized to solve the optimal equipment capacity with minimum annual carbon dioxide emissions. On the third stage, particle swarm optimization was utilized to solve the optimal operation strategy with minimum annual operation costs. A case of CCHP system used in a hospital building validated the effectiveness of this optimal method. Results show that this CCHP system designed by this optimal method is more energy saving, more environmental and more profitable than two CCHP systems separately designed by following the electric load (FEL) and following the thermal load (FTL) operation strategy.