Sanjiashi yiwen shuzheng and Sanjiashi yishuo were Feng Dengfu's major works about the Three Schools. Collecting and compiling lost texts of the Three Schools was the foundation of composing these books, though they were not written merely for that purpose. This paper focuses on Feng's endeavors at collecting and compiling lost texts (jiyixue). The two books were first organized around the Three Schools but were then reorganized according to the order of the three hundred poems. By no longer mechanically separating those collected writings into Three Schools, the books' structure reflected the evolution from Wang Yinglin's Shi Kao to Fan Jiaxiang's Sanjiashi shiyi. Feng expanded the methods of collecting and compiling lost writings, from directly citing the quotation to considerations of teacher-succession as well as inference and deduction. These methods increased the amount of collected materials. In Shuzheng, Feng Dengfu did not rank the value of the Mao tradition and the Three Schools, but in Yishuo, he was of the opinion that the Three Schools were far superior to the Mao tradition. His opinion was an obvious contrast to that of Fan Jiaxiang, who insisted on the Mao tradition's superiority. Moreover, Feng was highly appreciated by Ruan Yuan and greatly influenced by Wei Yuan; he was also deeply involved in the academic scene in the middle of the Daoguang period. His two books thus offer a significant testimony to the various aspects of the intellectual trends of the day. They are truly important works in the collection and compilation tradition of the Three Schools.