The invention discloses a method for preparing ruthenium dioxide for resistance paste. The method comprises the steps of preparing a ruthenium trichloride solution with the concentration of 0.01mol/L to 1mol/L and a quaternary ammonium salt solution with the concentration of 0.01mol/L to 3mol/L, dropwise adding the ruthenium trichloride solution into the quaternary ammonium salt solution under the condition of carrying out heating and magnetic stirring according to the mole ratio of 1: (3 to 5), stopping stirring until the pH value of the solution is 7 to 8 after dropwise adding is completed, washing obtained black precipitates with a centrifuge, carrying out filtering, and then, carrying out baking, thereby obtaining the ruthenium dioxide. According to the method, the used quaternary ammonium salt solution is alkaline and acts the action of a surfactant; and the ruthenium dioxide prepared by the method has the advantages of high purity, high particle size uniformity, good dispersity and the like, the synthesis conditions are moderate, the preparation cycle is short, the efficiency is high, impurity ions are easily cleaned, the number of required aftertreatment steps is relatively small, meanwhile, the operation is simple, and toxic gas cannot be generated, so that the range of application in the paste is wide, and the ruthenium dioxide can be used for preparing medium-/low-resistance materials.