Before estimating the functional depreciation of machinery and equipment, appraisers should analyze the determined replacement cost and substantial depreciation to see whether the functional depreciation factor has been deducted. If functional depreciation has been deducted, don't double-calculate; If functional depreciation is not deducted, and there is functional depreciation, the corresponding method should be adopted to estimate, and the evaluation cannot be omitted. In fact, the equipment replacement cost determined by the price index method contains functional depreciation factors, and the equipment replacement cost determined by the functional value method has deducted functional depreciation; The new rate determined by the fixed number of years method does not deduct the functional depreciation factor; Repair cost method can deduct all or part of functional depreciation.