唐代在文化思想上，採取了儒、釋、道三教並行的政策，佛教界亦受到此思潮的影響，與儒家之易學產生了會通的傾向，其中華嚴宗四祖澄觀之《華嚴經疏鈔》，就大量援引易學義理。澄觀於《華嚴經疏鈔》引用外典部分，散落於各品，並不集中，經筆者之統計發現，引用外典次數最多者為儒家之《周易》，茲分為三種類型來討論：（1）借用《周易》，闡明華嚴教理；（2）將《周易》視為外道；（3）以《周易》來解釋詞義。其中第一類，例句最多，也是澄觀引用《周易》的主要目的；第二類，例句最少，但說明了澄觀對於三教的態度，以及對於佛教所抱持的立場；第三類，則只是一般詞義的解釋，較沒有特殊意義。
澄觀之易學思想，主要參考玄學義理派的《周易正義》。澄觀引用《周易》的原典，以〈繫辭〉上下篇最多，共二十餘次，其哲理性、思辨性最高，可與《華嚴經》互相匹配。至於澄觀引用易學之注疏，以韓康伯注為主；其次為王弼注，又兼引《周易略例．明象》；孔穎達的疏則引用不多。

The cultural thought of Tang Dynasty combined the three sects: Confucianism, Buddhism and Taoism. This trend influenced Buddhism, and whats more, Buddhism combined itself with Yi-ology of Confucianism. For instance, Huayanjingshuchao quoted lots of Yi-ology. Instead of being shown in one part of Huayanjingshuchao, the citations appeared in different parts. Furthermore, Zhouyi was cited more than the books of the other sects. These citations related to Zhouyi can be classified into three types: borrowing Zhouyi to clarify the thoughts of Huayanjing, viewing Zhouyi as the thoughts of heretics, and using Zhouyi for explaining the meanings of the words. The first type not only had the most example sentences, but it was the main purpose for Chengguan to cite Zhouyi. As for the second type, though it had the fewest example sentences, yet it unfolded Chengguan’s attitudes toward the three sects and Buddhism. Regarding the third type, Chengguan just used Zhouyi to explain the meanings of the words without any special purpose.
Chengguan’s thought of Yi-ology mainly derived from the Metaphysical argumentation faction of Zhouyizhengyi. Chengguan cited the original text of Zhouyi, in which “Xici,” which has the highest philosophy and speculation as Huayanjing, appeared most frequently and it appeared about twenty times. Concerning Chengguan’s citations of Yi-ology, they originated mainly from Hankangbo, secondly from Wangbi, and also the “Mingxiang” in the Zhouyilueli, but only a few quotes came from Kongyingda.