The Theories and Methods (Preface and Postscript Collection of Rong Xinjiang) (Exquisite) by Rong Xinjiang is divided into two parts. Part I is a preface and postscript written for other people's works. Part II is a preface and postscript of his own works, which covers Dunhuang Tubo Studies, history of Sui and Tang Dynasties, history of Sino-foreign relations, history of Western Regions and other fields.Each preface and postscript summarizes the course of development of the subject, analyses the direction of development, evaluates the contribution of the work, and condenses the author's exploration and reflection on relevant research fields.