By means of a c1ass of recursive functions ? on I₊，this paper defines a c1ass of context-sensitive languages ＆ over the alphabet ∑={a}，and then presents a context-sensitive grammar schema generating the language of ＆ by a structured analysis method. Furthermore，an unified method and theory for grammar design of ＆ is formed. The methods and techniques discussed here can be generalized to grammar design of all other context-sensitive languages.