The invention discloses a distributed photovoltaic power generating capacity estimating system and a solar radiation data generation method, and is widely applicable to scientific research and engineering application in the area related to solar energy. A comprehensive calculating module utilizes a representative weather year and month method to acquire weather index data to calculate and analyze, an evaluated and quantized value acquiring module is used for overlapping and transforming total solar radiation data every day of the year generated in the comprehensive calculating module so as to acquire evaluated and quantized value, and a distributed photovoltaic power generating evaluating module compares the quantized value with a evaluation system to acquire a distributed photovoltaic power generating capacity evaluating result. The distributed photovoltaic power generating capacity estimating system and the solar radiation data generation method can be widely applied to various areas and weather conditions, the generated total solar radiation data every day of the year are representative, the evaluating result is objective and reasonable, and the requirement of distributed photovoltaic power generating planning engineering application can be met.