Abstract: This paper begins with the discussion of history,definition,and requirements of PDL, which stands for Program Design Languages,and then analyzes the necessity for the development of Ada-based PDL,its application fields,and its relation with Aria and software design methodology. Some important tools supporting Ada-based PDL are described and,as typical examples,several Ada- based PDL’s are given.At the end of the paper,pointed out are some problems which remain to be solved.