Abstract: The stability, reliability, safety and power quality of the power system are particularly important when grid-connected photovoltaics. Therefore, when building PV power systems and PV grid-connected systems, it is necessary to accurately recognize the main faults faced by PV systems. In this paper, the main faults of PV grid-connected are classified as DC-side faults and AC-side faults, and then the effects of line faults, open-circuit faults, MPPT faults, aging faults, grounding faults, arc faults, mismatch faults, and inverter faults on PV grid-connected systems are detailed, while the main fault detection methods in recent years are briefly reviewed to provide some reference and ideas.