The invention relates to a medium-and-long term new energy resource database construction method and system, and the method comprises the steps: carrying out the climate data simulation based on a pre-constructed multi-source meteorological data assimilation database and a re-analysis database, and generating a climate simulation data set; and integrating the climate simulation data set accordingto a preset classification scale to generate a medium-and-long-term new energy resource database. The medium-and-long-term new energy resource database construction method based on the multi-source data re-analysis technology is used for predicting the medium-and-long-term distribution condition of new energy resources, supporting large-scale development of new energy and avoiding a large amount of wind curtailment and light curtailment.