The invention discloses a photovoltaic module outdoor PID testing system and testing method. The system comprises a photovoltaic generation device and a water spraying subsystem; the photovoltaic generation device comprises multiple photovoltaic modules in grid-connected generation; the water spraying subsystem is used for spraying hot water to the surface of each photovoltaic module, thereby enabling two surfaces of the photovoltaic module to be covered by water films, the temperature of the hot water is 20-100 DEG C. The outdoor PID testing system can simulate outdoor high-temperature high-humidity work environment, thereby detecting the PID resistance of the photovoltaic module under the actual generation work condition.