In recent years, the large-scale integration of wind turbines featuring a strong uncertainty and weak supporting capability has posed a threat to the frequency security and stable operation of the new power system. To ensure the safe, high quality and economical operation of high proportion of wind power system, this paper proposes a multi-level optimal dispatch strategy considering the wind power ramping limit and frequency security constraints. First, considering the wind power prediction error and the requirements of wind farm grid-connection, the geometric description and characteristic analysis of wind power ramping in adjacent scheduling periods are carried out. Secondly, a station and system level joint dispatch structure considering day-ahead/intra-day/real-time multi-stage is proposed. A wind power station dispatch model considering wind power ramping limit constraint and a power system optimal dispatch model considering frequency security constraint are established. Finally, an example analysis is carried out based on the improved IEEE 39-bus system to verify the effectiveness of the proposed strategy.