In this paper, the characteristics of linearly tapered strip-line filters, where the even-mode and odd-mode characteristic impedances vary linearly with the same degree along the lines, are analyzed. The Impedance parameters of linearly tapered coupled strip-line, which is made by connecting two linearly tapered unsymmetric coupled strip-lines In cascade and the I:no input and output terminals are made equal, are obtained. Using the above parameters, the Image parameters of linearly tapered coupled strip-line filters are derived. The result of analysis shows that the line length can be made shorter and also the stop-band width between the fundamental and second pass-band becomes wider, compared with the coupled strip-line filters which use uniform strip-lines. Furthermore, the difference of impedance levels in the fundsmental and second pass-band becomes larger with the degree of taper of the lines. This property is unique, in comparison with the case of uniform or exponentially tapered strip-line filters.