Fractional order Butterworth filter derived from the conventional 3 rd order Butterworth filter by the transition of the ordinary derivative to the fractional one as in [1] is investigated in this paper. The change of the filter characteristics is studied depending on the order of the fractional derivative. Effects of the transformation on the components' behaviors of the filter is formulated. Design of the filter in the sense of choosing the filter parameters to satisfying the given specifications is described.