This article proposes a new time-based depreciation method using the accumulated depreciation rate function. The method can systematically compute the depreciation charge of each period, in every case where the charge is constant or decreasing or increasing, and solve the problems of depreciation methods currently used, by obtaining the accumulated depreciation charge at any given time. We can choose diverse rational depreciation types for the characteristic of every asset with the new method, and compute the depreciation charge with consistency in all cases where assets are owned for partial period.