A cabinet air duct, a cabinet assembly and a photovoltaic inverter are provided according to the present application, where the cabinet air duct includes a cabinet and an air duct arranged in the cabinet. The cabinet is provided with an air inlet and an air outlet that are in communication with the air duct. The air inlet is arranged on a first side surface of the cabinet, the air outlet is arranged on a second side surface of the cabinet, and the first side surface and the second side surface are two opposite side surfaces of the cabinet.