The invention provides an electric system peak regulating method based on wind power and hydropower. The method comprises the steps that a wind power output force characteristic curve is obtained and corrected; distribution checking is carried out on an equivalent load curve to obtain a density distribution function of the equivalent load curve; a peak regulation improvement factor curve is calculated; a capacity impact factor curve is calculated; wind curtailment power is used as a variable, a non-zero crossing of the peak regulation improvement factor curve and the capacity impact factor curve is calculated, and a wind abandoning power value corresponding to the non-zero crossing is calculated; electric system peak regulation is carried out by using the wind abandoning power value the largest wind abandoning power on the basis of the peak regulation rule of selecting wind abandoning preferentially and selecting water abandoning secondly. Peak regulation improvement factors and capacity impact factors are provided, the wind power and hydropower abandoning amount is reasonably distributed, the wind and water abandoning power value with the lowest cost is obtained through calculation, and the stable operation and optimal cost operation of an electric system are ensured. The method is simple and reliable, calculation is easy and convenient, and popularization is easy.