In the Tang Dynasty, the three sects, Confucianism,Buddhism and Taoism, were combined in culture and thoughts. Influenced by this trend, Buddhism combined itself with Lao-ology of Taoism. For instance, in Huayanjingshuchao, the citations from Lao-ology appeared in different parts rather than one part. Moreover, in Huayanjingshuchao, compared with all the other books of the other sects, Zhouyi was cited more, followed by the Taoist classics--Laozi and Zhuangzi. Therefore, “The Relationship between Chengguan’s Huayanjingshuchao and Yi-ology” had been discussed, and “The Relationship between Chengguan’s Huayanjingshuchao and Lao-ology” is explored as follows. First, these citations related to Laozi are classified into three types: borrowing Laozi to clarify the thoughts of Huayanjing, viewing Laozi as the thoughts of heretics, and adopting Laozi to explain the meanings of the words. Secondly, the first type had the most example sentences, and it was also the main purpose for Chengguan to cite Laozi. As for the second type, which has three instances, it unfolded Chengguan’s attitudes toward the three sects. Regarding the third type, which has two instances, Laozi is used to explain the meanings of the words with no special purpose. After inspecting the development of Lao-ology in the era, the two notes, Yuzhu and Heshanggongzhu, Chengguan had quoted are mainly introduced. The concepts of Lao-ology in the era which influenced Chengguan most are two. One is “Imitation of Nature,” the concept which Chengguan quoted most from Laozi and is the most important issue of ideological debating between Buddhism and Taoism in the earlier dynasty. The other one is that the specific concepts Chengguan quoted from Laozi are Cosmic View in Heshanggongzhu and Universe Generation in Yuzhu.