The main purpose of this study is to develop an interactive on-line learning system, which is to create the information technology instruction environment to help industrial vocational students to learn math. we hope to assist students to learn math by the convenience of the internet. according to an unofficial investigation in Taiwan, students hope teacher can provide the solving process and hints when they study math, therefore, this study has combined the features of internet, the scaffolding theory of L. S. Vygotsky and the elaboration feedback theory. we organize the main ideas of the limitations in calculus and develop an interactive on-line learning system. the features of this system are: 1. to organize the question styles, to provide students hints to solve the questions and to help students to learn the concept of the course. 2. to take the elaborations feedback and to help students solve the questions immediately. 3. the connect whit the information bank, to record students' learning time and to analyze students' myth for solving questions. 4. to provide the on-line test for encouraging students to do the active learning. 5. to provide the interaction function for students and teachers to share mutual experience. the following research is to analyze the entire question bank by item response theory (IRT) in order to make the well-structure test. to develop a humanized interactive learning system is our goal. we hope the concrete affection of this system can be evaluated.