Abstract:Through an investigation into the dialects of various counties and districts in Chong qing, the author of this paper has found that the mutual replacement of and h is different in different places. Roughly, there are five different types of such replacement: mixture of “xiao” group into “fei” group; all “fei” group mixed into “xiao” group; “fei’ group with the pronunciation x when they precede o, and “xiao” group being read as f when they appear before the vowel u and medial u; “xiao” group being read as f when they appear before the vowel u and medial u; no obvious rules of mixture of the two sound into each other. There are three main reasons for such replacement: high auditory similarity, deep influence from the vowel u and medial u, and geographical and migration factors.