The invention discloses a regional distributed photovoltaic fault diagnosis system and method for an access power distribution network. The system comprises a fault information detection sub-system, a fault data processing sub-system, a fault recognition sub-system, a fault model base sub-system, a fault alarm display sub-system and a fault feedback sub-system, wherein a photovoltaic grid connected point and power grid information are automatically obtained through the fault information detection sub-system and the fault data processing sub-system; fault information screening is carried out through classification, analysis and conversion; and the system is capable of automatically judging the fault type, analyzing the fault reasons, locating the fault position, automatically alarming at a fault point after judging the fault, and displaying detailed fault information according to the fault information processing result. The regional distributed photovoltaic fault diagnosis system provides a support for establishing a distributed photovoltaic power distribution network management system, and the operation security of the power grid is ensured.