This paper proposes a novel method for designing linear phase FIR digital filters with asymmetric transition band. The proposed filters have a form of piecewise exponential functions in frequency domain where transition characteristics is determined by giving only two fixed feature points. The design method was evaluated in two ways. First, we evaluated a designed asymmetric transition band filter, and the results revealed that evaluated errors of the proposed filters are equivalent to a well-known existing filters. Then, it was shown that three-channel filterbank with an asymmetric transition band and liner phase property can be implemented.