Abstract: With the increasing penetration of renewable energy, short-term energy storage technology represented by electrochemical energy storage will make it difficult to meet the demand for new power systems to consume renewable energy, and at the same time, flexibility will become the core and key to the operational characteristics of the system. Therefore, this paper proposes a joint long-term and short-term energy storage planning method considering the flexibility of supply-demand balance. First, for the characteristics of energy storage technologies in different time scales, this paper integrates the dual regulation of short-term power and long-term energy, considers the flexibility of supply-demand balance combines the price-based demand response mechanism, and establishes a joint planning model of long-term and short-term energy storage with the lowest annualized comprehensive cost of the system as the optimization goal. Second, to simplify the problem size, typical scenarios are extracted each month to re-sculpt the whole year's time sequence using a deep convolutional embedding clustering algorithm, and the model is optimally solved through two stages of capacity planning of wind, photovoltaic, and energy storage and flexibility calibration. Finally, the effectiveness of the planning method proposed in this paper in considering the economics and operational flexibility of a new power system with high penetration of renewable energy in the future is verified by using a region in eastern China as an example.