Abstract: This paper briefly introduces the implementation of a natural language (English) interface for anumerial-control automatic programming expert system dcvclopcd by our institute.The interface is nowrunning under the UNIX on Sun 3/4 or DOS on IBM/AT and is programcd in C language.It is composed of lexical analytical module,syntax analytical module,scmantic-pragmatic analytical module,object gcncration module,graphic simulation module and various knowledge bascs.The interface can acceptthe description of the pieceworks necded by the cxpert system and process some simple English languagephenomena.