Abstract: Unpredictable variations in the renewable energy generation give rise to power generation output unbalance, which could not be neglected in the economic dispatch issue. Aiming at this problem, by mean of analyzing two different kinds of characteristics for fluctuant uncertainty and intermittent uncertainty in uncertain variable changes, the concept of passive variable power output changing speed and relevant new constraint expression were constituted according to seeking the rigorous scene scope for the variations of load and renewable energy power generation based on the interval satisfactory degree constraint, and then the interval economic dispatching model of power system considering the intermittency was proposed. This research allowed power system economic dispatch to take into account both the demands for quantity and extent of uncertainties effectively in the decision for addressing and incorporating the renewable energy power generation, meanwhile, the robustness of the scheduling solutions was efficiently improved. At last, the correctness and effectiveness is verified by simulations on 10-unit system.