Abstract: When the penetration of wind and solar power reaches a high level, the monthly-to-seasonal energy supply-demand balance will become a critical challenge for the power and heating sectors. To investigate the seasonal energy regulation roles of coal power and seasonal energy storage, a research methodology for the transformation path of the power and heating sectors was developed that considered the interactions among electricity, heat and hydrogen, incorporating multiple temporal resolutions. This approach formed a multi-time-scale joint optimization model tool for long-term planning and short-term operation of the power and heating sectors, based on electricity and heat balance. The model captured the long-term development goals and short-term operational constraints of high-renewable electricity and heating systems. It can be used to study the roles of coal power and seasonal storage in addressing seasonal energy supply-demand imbalances and project the overall development pathways of the power and heating sectors.