Abstract: A high-precision solar resource assessment method based on a downscaling method for complex terrain includes steps as follows. Step (1): an average climatic field is calculated based on monitoring data of sunshine durations, climatic field interpolation results are obtained based on the average climatic field, and a climatic field is created. Step (2): a difference between data of the sunshine durations and the climatic field is calculated, anomaly field interpolation results are obtained based on the difference, and an anomaly field is created. Step (3): the climatic field interpolation results and the anomaly field interpolation results are overlayed. Step (4): bias adjustment is performed on the high-precision sunshine duration interpolation results obtained in the step (3) based on the monitoring data of the sunshine durations to obtain final results. Step (5): daily solar radiation is estimated based on the sunshine durations and extraterrestrial solar radiation.