The invention provides a method of assessing an optimum depreciation life of electric power equipment. The method comprises the following steps of according to association relations of preset new equipment benefits and a life limit, and old equipment earnings and the life limit, acquiring an association relation of old equipment maintenance cost and a failure rate and a corresponding constraint condition; determining a plurality of equipment to be assessed, acquiring historical fault data of each equipment to be assessed, obtaining a failure rate fitting curve of each equipment to be assessed, and further simulating Weibull distribution to acquire a shape parameter and a scale parameter of each equipment to be assessed corresponding to the Weibull distribution; according to the shape parameter and the scale parameter of each equipment to be assessed corresponding to the Weibull distribution, determining an association function of the failure rate of each equipment to be assessed, introducing an association relation of old equipment maintenance cost and the failure rate respectively so as to obtain an optimum depreciation life of each equipment to be assessed when the constraint condition is satisfied. In the invention, the optimum depreciation life can be analyzed; enterprise incomes are increased and enterprise losses caused by depreciation of assets are reduced.