The invention provides a simplified interpolation algorithm for improving the electric energy quality analysis precision of a digital transformer station. A three-batten interpolation algorithm is applied to expansion of electric energy quality monitoring sampling data of the intelligent transformer station, the three-batten interpolation algorithm is simplified on the basis of sampling characteristics to solve the problem that the three-batten interpolation algorithm is slow in calculation and needs relatively long time, and equally-spaced characteristics are used to simplify a calculation process and reduce calculation parameters; virtual sampling points are added to satisfy periodic requirements of three-batten interpolation, and a boundary condition calculation process is simplified; and a three-diagonal linear equation serves as a simplified batten equation, an equation set is solved in a chasing method, and calculation steps are reduced. The electric energy quality analysis precision of the intelligent transformer station can be improved, and the defects of complex calculation and long solving time of the traditional three-batten interpolation algorithm can be overcome.