Frequency lowering algorithms are the most effective and secure for improving the auditory identification capability of hearing-impaired patients. Through analyzing the current algorithms by the test of subjective auditory approach, in the paper we propose an adaptive algorithm combining slow playback algorithm with frequency transition algorithm. The algorithm can adaptively adjust playback ratio according to the signal spectrum structure to reduce the desynchronization in time region. Furthermore, a method of evaluating the playback ratio in noise is designed based on the frequency spectrum relation between noise and noisy signal. Results showed that compared with other frequency lowering algorithms, the proposed algorithm can improve the auditory identification capability from 15% to 20%. In addition, in the test for hearing-impaired person, the significant improvement on the average auditory identification capability is also obtained compared with the conventional hearing aid device.