Abstract: This paper describes the design and realization of a Pinyin Chinese character conversion software.The system is composed of two subsystems,the Pinyin automatic words segmentation subsystem and the grammatical analysis subsystem. The techniques of building a Pinyin automatic words segmentation subsystem is based on those of building automatic words segmentation system of written Chinese.Grammatical analysis of the subsystem consists of lexical analysis,phrasal analysis and syntactic analysis.Grammatical analysis is realized by using keyword driven bottom up.Phrasal analysis plays the most important part in grammatical analysis.The most important work in the grammatical analysis subsystem is to combine the phrases in different layers.