Abstract: ABSTRACT: Capsule oil storage tank is widely used in power transformer, which plays an important role in preventing transformer insulation oil from aging. In order to ensure the safe and reliable operation of the transformer, it is necessary to pay attention to the inspection of the oil level in the oil storage tank of the main transformer in daily operation. In particular, the operation of the transformer for a long time, attention should be paid to prevent the accumulation of gas storage tank caused by abnormal rise in the oil level. Based on the analysis and treatment of oil spill from the oil tank of a main transformer in a company, the causes of oil spill caused by abnormal oil level rise of the main transformer are analyzed, and the treatment of abnormal oil level rise of the main transformer without fault is summarized, and put forward the relevant technical requirements.