Abstract: With the transformation and upgrading of the traditional power system to the new power systems dominated by renewable energy, the increasing penetration of the renewable energy and the declining proportion of the traditional generating units have caused a shortage of flexibility in the power system. The demand-side resources such as electric vehicles, data centers, and P2X (power-to-X) provide the flexibility to the power system at multiple time scales, an important part of the flexibility of the new power system. First, the flexibility requirements of a bulk power system and the distribution networks at different time scales are described in the context of the high proportional renewable energy. Then, the regulation characteristics and application practices of the typical demand-side resources are compared and summarized, the application scenarios of the demand side resources are studied when supporting the operation and planning of multi-time scale flexibility requirements in the bulk power system and its distribution network with the high proportional renewable energy. Finally, taking the aggregation, the electrical carbon synergy, the quantification of the reliable regulation capability and the communication and information exchange standard as examples, the key technologies supporting the application of demand-side resources in the new power system are summarized and prospected according to the development focus of the demand-side resources in the future.