The invention discloses a method for improving insulation and thermal aging resistance of oiled paper of a converter transformer, which comprises the preparation steps of 1, conducting material selection and pretreatment; 2, preparing turbid liquid; 3, stirring the turbid liquid, specifically, mechanically stirring the turbid liquid obtained in the step 2; 4, preparing a mixed solution; and 5, preparing modified cellulose oiled paper, specifically, pouring the pulp in the step 4 into a filter screen for preparation and formation, manufacturing a modified cellulose paper board on a paper sheetformer after squeezing and dry calendering, and then putting the modified cellulose paper board into a constant-temperature and constant-humidity box for oil immersion treatment. The method can effectively improve the insulation and aging resistance of the oiled paper. In addition, the invention further discloses a method for testing the performance of the oiled paper of the converter transformer.According to the method, the electrical performance, the mechanical performance, the aging state and the like of the oiled paper under the long-term thermal aging condition can be subjected to experimental testing, and the influence of nano TiO2 doping on the insulation and aging resistance of the oiled paper is analyzed.