Based on the knowledge of hardware structure and working principle of solar photovoltaic plant,as well as the technical parameters and the grounding performance of lightning protection equipment,this paper categorize the lightning protection grades of solar photovoltaic plant in accordance with related lightning protection standards.A method to test the lightning protection in photovoltaic system is proposed with measuring equipment of relatively large output current,and different frequency & small current test combined with help of GPS.The photovoltaic cell matrix section and power transmission & distribution equipment are chosen to be the key areas to test the lightning protection.Expected values are listed for every technical parameter and compared with measured result.This test method is low in disturbance,safe in operation,accurate in GPS locating,thus is reasonable and practical to test and judge the performance of lightning protection and grounding equipment in photovoltaic system.