When the cell pack is tested, it need low ripple charging current to ensure the tester accuracy. It is very necessary to set proper DC filter which has excellent filtering characteristic and wide input/output range. The inner resistance of a cell pack is very small but the system is indefinite. If the DC filter is designed by the type of traditional matched filter, the flat-fading would inevitably occur. This would reduce the power transmission efficiency. This paper discussed the design philosophy of the non-matched filter and proposed a non-matched Chebyshev DC filter design method aimed at the special resistive-capacitive property of the cell pack. The method is proved to be correct and feasible by simulation.