In ancient China, "poem" was always considered as an important literary genre. As one of the most important elements of a poem, "rhyme" has enjoyed a wide recognition among poets for hundreds of years. Rhyme has been highlighted in poetry ever since the times of ancient folk songs. Being an indispensible element in poems, "rhyme" plays an essential role in the expressive function. The essential vowel in a compound vowel (pronounced as "Yunfu" in Chinese), the most important part of "rhyme", is also potentially connected to the emotion of the poem.