Compared with the shang and qu tones, the yinping and yangping tones in the Jianghuai dialect maintain a consistent and uniform pattern of development. The yinping tone in most of the Jianghuai dialect is low-falling. The yangping of Hongchao and Tairu districts is high-rising but that of Huangxiao district is high-falling. Based on a close observation of the relevant dialects and on theories of language contact, this article draws the conclusion that the yinping and yangping tones in the Jianghuai dialect have different derivations. Yinping maintains the characteristics of old-time Jianghuai dialect while yangping either directly adopts the characteristics of surrounding dialects or has undergone changes caused by the influence of those dialects. Timing differences of devoicing of the initial consonants might be a key factor leading to the present situation of the yinping and yangping tones in the Jianghuai dialect.