Explain in detail. We try to make some supplements from the perspective of the change of aesthetic thought of the times, so that our understanding of the problem is more comprehensive. The Mid-Tang and Yuanhe period is an important stage in the development of Tang poetry, and it is also a turning point in the great changes of China's ancient poetry. A Qing scholar Ye Xie pointed out: "Zhenyuan, Yuanhe Poetry, Han, Liu, Liu, Qian, Yuan and Bai are all extraordinarily dangerous and are the key to the development of ancient and modern poetry. Later generations called it poetry, and there was nothing in the chest, which was called the middle Tang Dynasty. Those who don't know this "zhong" are the "zhong" in ancient and modern times, not the only one in the Tang Dynasty. After thousands of years, everything is broken. " Zhu Tingzhen once said: "With the decline of the calendar, the style is getting better and better, and the atmosphere is getting worse. Therefore, Long Valley wins in grandeur, Bai Yuan wins in simplicity, arts and sciences wins in beauty, and suburban islands wins in preciseness. Although they have different personalities, they can all form their own situation and are trying to change. " In fact, Ye's Adventures and Zhu's Seeking Change are the multi-directional aesthetic exploration of Tang poets and the major changes in the aesthetic trend of the times. Many changes and turning points in China's ancient poetry occurred in the middle Tang Dynasty, from elegance to vulgarity, from emotion to reason, from maturity to innovation, from muddy to engraved dew, and so on. The theory and creation of Bai Juyi's new Yuefu poems are closely related to the historical process of this turning point If we make an in-depth analysis of Bai Juyi's new Yuefu poems, we will find that it is obviously different from the traditional satirical poems marked by elegance and contention. Although Bai Juyi once said, "What about poetry? Six meanings are shared. Elegant and elegant, I have never tasted empty talk. " (Reading Zhang Ji's Ancient Yuefu) However, none of his ten poems reciting songs in the middle of the Qin Dynasty was written by means of metaphor, and only a few of his fifty new Yuefu poems, such as Qin Jiliao, used metaphor, which is a noteworthy phenomenon. When Bai Juyi summed up his own creation, he talked about his satirical poems many times, such as "Speaking with Quality", "Speaking Straight and to the Point" (preface to the new Yuefu Poetry), "Excited by Meaning but Heavy by Quality" (nine books at the end of Yuan Dynasty) and "Excited by Words if the meaning is too sharp" (ten preface to answering poems). The quality is straightforward, naturally abandoning the gentle and honest traditional aesthetic view of "seeing the loss of today, not daring to criticize, taking analogy as an example" (Han Zhengxuan's "Li Zhouguan's Pure Note") and following a kind of "not comparing, not hiding" $ #%&; ! ())' s new creative principle. Therefore, the writing method of Bai Juyi's new Yuefu poems is an intentional new exploration, not an accidental phenomenon. It should be noted that under the influence of the aesthetic trend of the times, the authors of new Yuefu poems began to pursue and create a new poetic style that can reproduce real life more directly and truly and is full of fighting spirit. It is not a repetition of the traditional old tune of "elegance and struggle", but a new voice of the times of "doing things for the times"; It no longer regards the spiritual world of the subject as the main object of expression, and its fundamental purpose is to reproduce the objective life itself. Many characteristics of Bai Juyi's new Yuefu poems, such as popularity, simplicity, eagerness and verification, are all related to this. In connection with the rise of legendary novels in the middle Tang Dynasty, the prosperity of long narrative poems, the appearance of Qu Zi's poems and the spread of scripts and variants among the people, it can be said that this is a transfer trend from traditional expressive literature to emerging reproducible literature. If we analyze Bai Juyi's theory and creation of new Yuefu poetry in this historical trend, we may be able to understand its gains and losses more objectively and make a more accurate and comprehensive evaluation of its advantages and disadvantages.