The invention discloses hot rolled H-shaped steel for a vanadium-niobium microalloyed weather-resistant electric railway overhead contact system strut and a preparation method thereof. The preparation method comprises the following steps of A, desulfurization conducted through molten iron pretreatment; B, molten steel smelting; C, deoxidization alloying; D, molten steel refining conducted through an LF furnace; E, molten steel casting; F, billet heating, G, billet rolling; H, rapid cooling after rolling; I, natural cooling after rolling; J, H-shaped steel finishing. The hot rolled H-shaped steel has the advantages of high strength, uniform and fine microscopic structures, weather resistance and the like; in the smelting process, microalloy of vanadium and niobium is added, structural grains can be refined, the strength can be improved, and at the same time, the toughness and plasticity of the steel are effectively improved; Cu, Ni and Cr are added, so that atmospheric environment corrosion resistance is effectively improved.