The invention relates to a dust accumulation state estimation monitoring system of a photovoltaic power station and a method of the dust accumulation state estimation monitoring system. The dust accumulation state estimation monitoring system comprises a reference photovoltaic module, a DC/DC converter, irradiance sensors, a signal acquisition module, a signal processing module, a wireless transmission module and a monitoring platform, wherein models and parameters of the reference photovoltaic module and a photovoltaic module for a power station are same, the DC/DC converter is used for enabling a working point of the reference photovoltaic module to change according to a control signal, the signal acquisition module is used for acquiring a working current and a working voltage of the reference photovoltaic module, the irradiance sensors are respectively arranged on an upper surface and a lower surface of glass and are used for respectively measuring irradiation strength during no dust accumulation and dust accumulation, the wireless transmission module is used for uploading voltage processing data, current processing data and irradiation processing data of the reference photovoltaic module to the monitoring platform, and the monitoring platform is used for analyzing data, estimating an integral dust accumulation state of the power station and reminding a maintainer. By the dust accumulation state estimation monitoring system, the power loss caused by dust accumulation can be estimated, the temperature influence is excluded, and the estimation on dust accumulation is accurate to a module level and is objective, accurate and comprehensive.