HanYu, as a famous poet and literateur, has always drawn many researchers’ attention. Liu Xianxin’s DingHan makes comment on HanYu and his books, which has many fantastic views. As the book hasn’t been published so far, few people know the book. With the publishment of Tuishishu, its academic value is worth further discussing. This paper introduces the book DingHan on the writing reason and the style，and concludes HanYu’s behavior judgment and Hanyu’s peotry prose with the specific review of Liu Xianxin. Behavior judgment is shown in three aspects: advocating Confucianism and rejecting Buddhism with speciosity; begging the powerful and damaging Confucianism; commenting unjustly and recording untruthfully. On Hanyu’s peotry and prose, Dinghan contains appreciation and classification. 