Abstract: From the requests of Turbo-codes' coding and decoding, interleaver's relativity is discussed, and the performance of interleaver design affecting the hamming distance of Turbo-codes is analyzed. Relativity is proposed as a criterion. Based on the criterion, a new interleaving method of inverse diagonal is introduced. Because the relative coefficient of new method is zero and the length of interleaving is short, Turbo-codes can get satisfying error correcting. The conclusion is proved by simulation.