Abstract: As the "dual carbons" (namely, carbon peak and carbon neutrality)goal progresses, the proportion of renewable energy in power grids is expected to increase significantly. Consequently, conventional transmission methods of bases will no longer meet the requirements of receiving grids. To address this issue, a medium- and long-term optimization method for wind/solar/storage bases has been proposed, considering both credible capacity and peak shaving demands of receiving power grids. Regarding credible capacity supply, this method comprehensively considers the credible power supply during annual peak load periods and daily highest net load periods. The power supply capacity of the base is strengthened in these two aspects within base transmission. For participating in the peak shaving of receiving power grids, this method introduces the concept of shared absorption space between wind/solar from both bases and receiving power grids. Base energy storage is utilized to convert wind and solar power output to periods when peak shaving pressure on receiving power grids is minimized. The calculation results demonstrate that the proposed method is adopted to significantly enhance various transmission benefits for large-scale wind/solar/storage bases and reduce the abandoned power. The proposed model has been validated to maximize the role of base energy storage in ensuring supply reliability and peak shaving needs, thus providing a more suitable base transmission curve for these requirements.