Mr. Liu has been engaged in the appraisal and research of ancient paintings and calligraphy for more than 70 years, with remarkable achievements and outstanding contributions: he participated in the "China Ancient Painting and Calligraphy Appraisal Group" organized by National Cultural Heritage Administration twice and went to cultural relics collection units in 25 provinces, municipalities and autonomous regions to appraise and appraise more than 60,000 pieces. In two large-scale monographs, Catalogue of Ancient Paintings and Calligraphy in China and Catalogue of Ancient Paintings and Calligraphy in China, the results of his painstaking research and appraisal conclusions are integrated, which are enough for future generations to learn from. When he cleaned up and identified tens of thousands of Ming and Qing letters collected by the Palace Museum, he found a large number of letters with important literature value. Among the paintings and calligraphy classified as non-cultural relics, first-class national cultural relics such as Blind Picture by Liu Jiequn of Song Dynasty, Landscape Axis by Yuan Dynasty and Five-character Poem Axis by Zhao Mengfu of Yuan Dynasty have been discovered successively, which saved precious cultural relics for the country and avoided heavy losses, reflecting the noble quality of the older generation of cultural relics workers in fulfilling their duties. After 1970s, he went to the United States, Hongkong, Taiwan Province and other places for academic exchanges, and enjoyed a high reputation in the field of cultural relics museums at home and abroad.

Mr. Liu is eager to learn quickly, rigorous in his studies and meticulous in his textual research. See the calligraphy and painting, diligent in taking notes and good at summing up. The identification of calligraphy and letters in Ming and Qing Dynasties has a unique feature: it is not only familiar with the calligraphy and paintings of "Xiaomingtou", but also can find and solve problems from nuances. He has written and published more than 30 important academic papers, including Notes on Some Issues of Badashanren's Painting and Calligraphy, Notes on Some Issues of Badashanren's Painting and Calligraphy, Discrimination of Wang Chong's Calligraphy Works, Discrimination of Zhu Yunming's cursive script and counterfeit book, Analysis of Jin Nong's handwriting and ghostwriting, and Zhang Daqian's fake celebrity painting and calligraphy, etc., which are not only detailed in historical materials, but also rigorous in argumentation. Although it has been revised and supplemented on the basis of other people's research results, it has made a major breakthrough. This book is an important reference for the study of art history and the appraisal of calligraphy and painting, which is a collection of a large number of physical materials reviewed and carefully appraised by the author himself. Mr. Liu's "Atlas of Appraisal of Calligraphy and Painting in Past Dynasties in China" also uses a lot of physical materials to analyze all aspects of calligraphy and painting forgery, which is quite distinctive and is another masterpiece of his improvement and development of traditional appraisal experience.