The invention discloses a method for building an association relation between the irradiance and coordinates of photovoltaic assemblies under various weather changes. The method comprises the specificsteps of determining coordinate positions of the photovoltaic assemblies and light sensors; determining a shooting position and a moving mode of an image acquisition device; respectively acquiring irradiance data of each coordinate position of a photovoltaic array in sunny, overcast, rainy and cloudy weather conditions; enabling the irradiance of each assembly of a photovoltaic cell panel to respectively correspond to the current coordinates thereof, and building a real-time irradiance matrix of the photovoltaic assemblies. The method disclosed by the invention performs comprehensive analysisand detection on the irradiance of the photovoltaic assemblies under various weather conditions, thereby improving the accuracy and speed of local shadow distribution range and irradiance measurement, being conducive to accurately predicting the photovoltaic output, improving the system safety and stabilizing the operating capacity.