Abstract: With the large-scale wind power and other renewable energy are integrated into the power grid, their uncertainty and volatility have threatened the operational security of the power grids. In view of this problem, the robust dispatch and the interval dispatch methods conventionally adopted cannot consider the constraints of the system power balance and the line power flow safety simultaneously under the uncertainty. Thereby, in this paper, regarding the wind power output as an interval number, the interval economic dispatch model considering the shiftable and reducible flexible loads is established, where the constraints of power balance under the wind power limitation scenarios, the constraints of system power balance under the uncertainty, and the line power flow safety constraints under the uncertainty are taken into account. In order to solve the model, an interval economic dispatch approach based on the security limit method (SLM) is proposed, in which the optimizing-scenarios method (OSM) is used to solve the interval DC power flow, obtaining the safety limit. Then, the interval optimization model is transformed to a deterministic quadratic programming model through the SLM. Adopting the IEEE 118-bus system for testing, the results show that the dispatch strategy obtained by the proposed method is able to satisfy the power balance constraints in the extreme scenarios and ensure the safety of the line transmission power for all the uncertain scenarios, while reducing the dispatching cost. In addition, the operating cost can be saved by reducing the load or curtailing the wind when the wind power output is small or large, and the flexible loads here play a role of peak cutting and valley filling, which provides a technical support for the safe and economic operation of the power systems incorporating renewable energy.