Abstract: Building solar photovoltaic power generation system can effectively improve the utilization of roof.Moreover，it can provide backup power for daily life and office. In this paper，to regulate the design of such small power generation systems，the study on 60 kW photovoltaic grid-connected power syslem set on the building roof of Kunming Melallurgy College was carried out.Under the analysis of regional climate conditions such as solar illumination，the serial and parallel scheme，array spacing，installation method and basic design of the photovoltaic module were analyzed. The result confirmed that the generation efficiency of the studied photovoltaic power system can reach 83.8%. However，there is also a serious design problem that the system counlercurrent is not considered effectively in the studied system.

Key words:  building, photovoltaic power, grid-connected, inverter, MPPT( maximum power point tracking )