Abstract：Transformers are the key apparatus in the oil field power system. For most transformers are placed outdoors, the lighting accidents happen frequently. This paper introduces the lighting protection measures for the transformers in oil field and analyzes the grounding mode, including the arrester, transformer shell, the neutral point of low voltage side grounding independently and grounding together. And it focuses on the effect of grounding mode on the lighting protection performance. Meanwhile, it calculates the effect of the grounding wire reactance and grounding resistance theoretically. Then, it comes to the conclusion that it is propitious for improving the lighting protection performance by grounding together mode and reducing the grounding reactance and resistance. In the end, the simulating results prove the validity of the analysis conclusion.