Abstarct: Deferential Algebraic Equations (DAE) has numerous applications in various sciences which different methods and approaches are applied to get to a faster answer for their solutions. One of the presented methods is the Fractional step method for deferential algebraic equations with indices 1 which is studied in this research. In chapter 1, the concepts and definitions are explained and we have a short review of the applications of deferential algebraic equations. In chapter 2, at the beginning, the solution of deferential algebraic equations with indices 1 is presented, their errors are surveyed, and, afterwards, this method is generalized for deferential algebraic equations for indices 2. In chapter 3, this method is studied for compressible and incompressible Navier-Stockes equations and its algorithm is presented for this method. In the final chapter, first , semi-Lagrangian method for the Shallow Water equations is investigated. Next, we conclude that the presented Subtracting Fractional method in this research leads us to a faster answer to the Shallow Water Equations.