The invention discloses a transformer insulation defect analysis method based on a partial dielectric loss test. The dielectric loss test is widely applied to the analysis and diagnosis work of a transformer insulation state, but a traditional dielectric loss test method only tests the dielectric loss of a winding-iron core/a clamp/ground, and due to the fact that a negative method of wiring is usually adopted due to the limitation that a main transformer is grounded, the test accuracy is poor, and defects of a specific position cannot be effectively judged. According to a typical structure ofa large power transformer, partial testing is carried out on the dielectric loss between the transformer winding-iron core, winding-clamp and different windings by using a method of positive wiring for reducing the voltage, and combined with the analysis of an electric field coupling effect between various partial insulating media, accurate analysis and defect positioning are carried out on insulation defects between various components of a transformer. The transformer insulation defect analysis method proposed by the invention has higher defect detection efficiency and positioning accuracy.