In this paper, fluid flow and heat transfer over a three-dimensional staggered circularpin-finned tube bundle heat exchanger surface have been numerically investigated. The effects of six geometric parameters and pin-fin arrangement in the flow direction on the thermo-hydraulic performance are investigated in details by adopting the performance evaluation plot of enhanced heat transfer oriented for energy-saving. The results show that the pin-fin diameter d, pin-fin length H, and pin-fin number around the tube N have positive effects on improving thermo-hydraulic performance, but the transverse tube pitch S 1 and the fin axial pitch S 1,pf have negative effects, whereas the longitudinal tube pitch S 2 and the fin arrangement in flow direction (in-line or staggered) have little effects.