In the regional electrical market of Northeast China， before day-ahead transaction being opened， the optimization of daily dispatch scheduling not only deals with the universal problems， such as normal constraint conditions， but also has its own particularity that the daily electricity decomposed from yearly or monthly bided must be ensured， as well as the equivalency of load rate of each power plant， to embody the impartiality. For this problem， the model of daily dispatch scheduling before day-ahead transaction being opened is built. Because of the advantage of primal-dual interior point algorithm in dealing with the constraint of inequality， combining time coupling pair decoupling method with primal-dual interior point algorithm， the peculiar problems are dealt by the first method， and the universal problems are dealt by the second， to achieve the mutual supplement of advantages. This optimization algorithm appropriately adapts to the character and requirement of this model. The result of typical example shows the concision and availability of this method.