The invention discloses a day-ahead plan computing method based on a distributed design. The method comprises the main steps of carrying out interactive computing on a master station and substations; submitting a next-day power curve to the master station through the substation, wherein a horizontal axis of the next-day power curve is time, and a longitudinal axis is a predictive power value at a corresponding time frame; summarizing all next-day power curve data submitted by the substations through the master station, judging whether the data meets the operation requirement of the master station, if yes, finishing computing, and otherwise, returning deviation data between the summarized next-day power curve data and the operation requirement of the master station to the substations; adjusting electricity generation and electricity utilization plans according to the deviation returned by the master station through the substations, re-computing a next-day power curve, submitting to the master station until the master station judges the operation requirement is met, and finishing computing. According to the day-ahead plan computing method based on the distributed design provided by the invention, a distributed design mode is adopted, and models are dispersed in the master station and the multiple substations, so that a computing model scale is greatly reduced, and the computing speed is greatly improved.