The invention is a principal component analysis based capacity optimization planning method for a pumped storage power station, which is characterized in that it includes: establishing a comprehensive evaluation index system for the capacity planning of a pumped storage power station, generating a capacity planning scheme for a pumped storage power station, and constructing a comprehensive evaluation Index matrix, convert the comprehensive evaluation index matrix to the same trend, perform standardized transformation on X′, calculate the correlation coefficient matrix for the comprehensive evaluation index matrix after the standardized transformation, calculate the variance contribution rate and cumulative variance contribution rate of the principal components and select Principal components, calculation of the selected w principal components, calculation of factor loads, comprehensive evaluation of each alternative, and determination of the optimal planning capacity of the pumped storage power station. It has the advantages of scientific and reasonable method, simple and practical, fast calculation speed and higher precision.