Excessive transformer losses can cause local overheating, insulation degradation, and other issues. These effects are further aggravated when the oil tank shielding design is suboptimal. Regarding these issues, this paper proposes a hybrid shielding structure. A three-dimensional model of a 220kV transformer was constructed in the article, and the loss distribution of the transformer under single material and mixed material shielding was analyzed and calculated through finite element simulation. After calculation and analysis, a hybrid shielding structure was proposed, which involves laying copper shielding at the oil tank and adding a layer of magnetic shielding material with a thickness of 3mm. Simulation results showed that the hybrid shielding structure can effectively reduce transformer stray losses.