The invention discloses a design method of a combined wing section blade of a horizontal shaft tidal current energy water turbine. The method comprises the steps of researching the hydrodynamic performance of a conventional wing section and the hydrodynamic performance of a bionic wing section separately, combining a conventional blade wing section with the bionic wing section according to the function of all blade elements in the blade, and designing out a combined wing section blade which is superior in performance; obtaining a three-dimensional digital model of a fish fin, selecting section contours of different positions of the fish fin as bionic fish-fin wing sections, selecting a bionic fish-fin wing section through analysis software, exporting the bionic fish-fin wing section and required two-dimensional coordinates of the conventional wing section, optimizing blade elements of the designed blade, obtaining parameters of each blade element, making the bionic wing section and the required conventional wing section correspond to the blade elements, converting the three-dimensional coordinates of the wing section into three-dimensional coordinate data, importing the three-dimensional coordinate data into three-dimensional design software, conducting setting-out treatment, and finally generating the combined wing section blade. By means of the design method, the hydrodynamic performance of the combined wing section blade is made to be superior, and the energy-obtaining efficiency of the water turbine is remarkably improved.