Paper presents the methodology of 3D optimization of a curved shape of the blades of H-Rotor type wind turbine. Original unsteady proper orthogonal decomposition (POD) approach was employed together with the radial basis function (RBF) to build an reduced order model of operating wind turbine that was further applied to optimize blades shape. The reduced order model was built based on the full-scale transient 3D CFD models of working wind turbine across the wide range of design points. The definition of rotors topology was based on FEA analysis of deformation due to centrifugal force and clearly defined shape parameters. The developed low-order model was validated against the full-scale unsteady CFD results and it indicated the high accuracy of ROM. The developed methodology allowed to decrease a few orders of magnitude the computational time for simulation of vertical axis wind turbines. Hence, it allowed us to carry out 3D shape optimization of the wind turbine blades with negligible time effort.