The invention provides a preparation method for modified insulation paper with improved direct-current space charge characteristics. The preparation method comprises the following steps: 1) preparation of paper pulp suspension; 2) preparation of a modified nanometer ZnO solution; 3) blending of nanometer ZnO with paper pulp; and 4) molding and calendering of the insulation paper. According to the invention, through modification of nanometer ZnO particles, the insulating properties of the insulation paper are improved and dissipation of space charges of the insulation paper is accelerated, so the space charge characteristics of the insulation paper are improved; through surface modification of the nanometer ZnO particles, the dispersity of the nanoparticles in a mixed solution of the nanoparticles and the paper pulp is improved, which facilitates formation of a more effective interfacial region between the nanoparticles and cellulose; and a formula for the modified insulation paper is simple, a nanometer filling material is low in cost and the preparation method is easy to operate.