Liu Yuxi and Liu Zongyuan were bosom friends and supported each other through ups and downs throughout their lives. They constantly exchanged letters and poems to console each other while being in exile in remote wilderness on political grounds. From the day they launched the innovation movement, they introduced each other as bosom friends. They fought against the unfortunate fate and the attack of hostile forces together. They encouraged each other in their lonely days. They expressed their emotions by letters and poems. The period when they were relegated again was the peak of their antiphon poetries. On the eve of the departure, they chanted and sang their antiphon poems, which were the embodiment of their intimate friendship. Liu Yuxi and Liu Zongyuan resided in Lianzhou and Liuzhou respectively. They communicated frequently, discussing philosophy, literature, medicine, calligraphy and other topics together. Maybe it was because they didn't want to pour too much sorrow into each other, nor did they want to transfer too much negative energy to each other, the antiphon poetries between them didn't focus on expressing feelings in these four years (815-819). They consciously used various genres to demonstrate their writing ability, and avoided the monotony and rigidity of the form of poetry. Another vital part of their antiphon poetries was the discussions about Chinese calligraphy, which are not only the remarkable exotic flowers in the garden of Tang Poetry, but also priceless historical records of Chinese calligraphy. Liu Yuxi and Liu Zongyuan both loved calligraphy, and Liu Zongyuan was more wrapped up in calligraphy. The theme of calligraphy does not require timeliness, also they didn't worry about whether it was politically correct or not. These poems about calligraphy were more relaxed and livelier than those antiphon poetries on other subjects. They teased and encouraged each other in these poems from time to time. They used many allusions and they gave full play to the functions of the antiphon poetries in mutual encouragement and entertainment. In 819, Liu Yuxi's mother died. At the same time, he received the obituary of Liu Zongyuan's death. This sudden double blow made Liu Yuxi very sad. In the process of editing Liu Zongyuan's anthology, he always sighed for his late friend who died young， and the yearning for him was deepening day by day. After Liu Zongyuan's death，Liu Yuxi and BaiJuyi first met in Yangzhou. Bai Juyi replaced Liu Zongyuan's original position in Liu Yuxi's heart，and became the most frequent friend with him. Especially in his later years when he was idle in Luoyang, there was more and more interaction between them. The number of antiphon poetries between them was huge. But the emotion of these poems was not as profound as those between Li Yuxi and Liu Zongyuan. In this sense, Liu Yuxi's and Liu Zongyuan's antiphon poetry were the kind of ″absolute sound″.