This essay aims to clarify the significance and importance of distributed Photovoltaic (PV) power plant on-site testing. Basing on the specific requirement of distributed PV power plant, the suitable testing contents and methods have been proposed. According to the on-site research for distributed PV power plant, and combined with one 350kWp roof-PV power station testing case, the feasibility and importance of on-site testing technology for PV power plant have been proved. Those testing contents and methods could supply the technological base and practice evidence for relevant standards, and support the PV plant’s grid-connected operation steadily.