Sawndip, mainly derived from Chinese characters while including some self-initiated characters, is a kind of national writing system for ancient Zhuang people to record their languages. This dissertation aims to explore these issues: the composition and origin of this writing system, the self-initiated characters and the derived characters in Sawndip, based on Sawndip Sawdenj, the most important dictionary available at present about this writings.This dissertation is divided into five chapters:Chapter I is an introduction. This part presents a detailed review of the researches on Sawndip especially of those since the foundation of the People's Republic of China, in which the main approaches and general stages of the study history is described, and the major fruits and problems under-discussed and need more efforts are pointed out. And approach and theories used in this dissertation are introduced.Chapter II deals with the composition and the origin of Sawndip. This part discusses the composition of Sawndip. It is argued that there are self-initiated characters in ancient Zhuang's writing system. There are several possible origins of Sawndip from the point of view of general graphology, ie., it is quite possible that it came from Chinese characters, primitive drawings, the primitive symbols and Tattoo etc. The estimated time when it came into existence, the inventors and genealogy of Sawndip are also discussed.Chapter III gives a study of the self-initiated characters in ancient Zhuang people's writing system. This part mainly analyses the self-initiated characters in Sawndip Sawdenj and explains some features of it.Chapter IV discusses the derived characters in Sawndip Sawdenj. This chapter analyses the derived characters by means of quantitative analysis and synonymy comparison, and the types of derived characters in this writing system.Chapter V is the last part of this dissertation. In this part, some conclusions are given, and some topics to be talked about in the future are brought about.