The invention discloses an equipment unit capacity value analysis-based power equipment purchasing method. Based on collected historical defect data of power equipment and corresponding manufacturer information, the confidence degrees capable of objectively and accurately reflecting the defect rates of the power equipment of different manufacturers is calculated firstly, and then according to theconfidence degrees, annual average defect rates of the power equipment of the different manufacturers since operation are calculated, so that a defect rate growth model capable of calculating the defect rates of the power equipment in future years is obtained, and the defect rates of the power equipment in operation for the same years can be calculated based on the defect rate growth model and arecompared; and in addition, the influence of change capable of scientifically reflecting load demands on purchase price is considered for avoiding unit capacity value of cost exception, finally the defect rate growth model and the unit capacity value are comprehensively considered, and corresponding weights are set to obtain purchase weights of the power equipment, so that a reasonable and comprehensive purchase policy is established.