The invention discloses an electric power spot market clearing calculation method based on multi-strategy fusion dimension reduction, and the method comprises the steps: firstly obtaining a power gridrange and a calculation period for carrying out the clearing calculation of an electric power spot market, and determining a calculation boundary; then carrying out merging analysis of similar time periods, and reducing the number of time periods for entering clearing calculation; establishing and solving a relaxation safety constraint unit combination model, carrying out invalid start-stop variable identification and effective safety constraint identification according to a calculation result, and reducing the number of start-stop variables and safety constraints entering clearing calculation; establishing a time period merged security constraint unit combination dimension reduction clearing model, and quickly solving to obtain a unit combination result; and carrying out full-time-periodeconomic dispatching and safety check analysis based on a unit combination result, adding the out-of-limit time period and the monitoring section into a unit combination dimension reduction clearingmodel, and finally obtaining an electric power spot market clearing result through iterative computation.