The invention provides a porous tungsten trioxide coated modified positive electrode material and a preparation method thereof. A surface of a positive electrode material is coated with tungsten trioxide, chemical formula is LiNi0.5Mn1.5O4/WO3, and the porosity of the porous tungsten trioxide is 8-15%. The preparation method comprises steps that firstly, the LiNi0.5Mn1.5O4 is prepared; secondly, H2WO4 is dissolved in hydrogen peroxide and deionized water to prepare a 0.8-1.0 mol/L solution, and WO3 sol is formed by heating in constant temperature water bath; polyethylene glycol is added to theWO3 sol and stirred and ultrasonically dispersed to obtain precursor solution; the LiNi0.5Mn1.5O4 is added to the precursor solution, stirred uniformly and then dried and sintered to obtain the porous tungsten monoxide coated modified positive electrode material. The method is advantaged in that the surface of the positive electrode material is coated through the porous tungsten trioxide, side reactions are suppressed, and cycle performance of a battery is improved.