In this paper, we present the theory of computers and mathematics education based on the concept of microworlds for mathematics education. We lust look back some previous papers published in the journal of the Korea society of mathematical education series A and else where. Then we present the new view points regarding mircroworlds and mathematics curriculems, microworlds and mathematics teaching and teaming, microworld based problem centered teaming, and microworld based diagnostics and debuggings. We use JavaMAL microworld that is designed to make LOGO and dynamic geometry system in one microworld to give some examples to explain the necessary mathematics educational needs fur designing microworlds for mathematics education. The JavaMAL microworld is a web based microworld that is programmed using JAVA, and the user on use script language, menus, keyboard, and mouse interaction to use the environment.