This paper establishes a model under the transformer losses and a model under oil-immersed transformer condition life lost in harmonic decomposition;The transformer losses and loss of life are calculated under the conditions of harmonic, and it impacts on the theoretical analysis proposed harmonic losses in transformers and transformer loss of life harmonic current distortion and load rate, it also studys the variation of harmonic loss and loss of life in different harmonic distortion and load rate; For the development of targeted measures to improve grid efficiency and economy, and further effectively protect the interests of all parties and users of the electricity sector has an important theoretical value and practical significance.