The invention relates to a distributed photovoltaic distribution network monitoring system and a control method thereof. With the system and method, a defect that the existing photovoltaic distribution network system can not be monitored effectively can be overcome. The system comprises a background control terminal, a main power distribution circuit and a plurality of distribution lines that are connected in parallel to the main power distribution circuit. Photovoltaic modules are connected to the distribution lines and are connected to the main power distribution circuit by the distribution lines. A low-voltage JP cabinet is installed on the main power distribution circuit; and a current transformer is installed inside the low-voltage JP cabinet and is also arranged on the main power distribution circuit. In addition, the system also includes an islet monitoring device and a plurality of photovoltaic monitoring devices; the islet monitoring device is installed on the main power distribution circuit; and the photovoltaic monitoring devices are installed on the distribution lines. According to the invention, a photovoltaic area monitoring system is established and all photovoltaic generation devices distributed on the distribution lines are managed in a centralized mode to complete unified distributed photovoltaic regulation of the distribution lines.