This study is about developing and testing the effectiveness of Computer Assisted Instruction (CAI) through multimedia in mathematical representations. Features that are developed using the hippo animator provides learning instructions with the tutorial model. The principle of self-regulated learning and mastery learning are both the strategy in learning to ensure students to be able to learn to be self-sufficient and complete. The principles of reliability, usability, maintainability, compatibility, reliability, reliability, interactive and communicative are carried out to assess multimedia well designed in terms of interfaces to maximize mathematical representation. For these purposes, R & D was selected in this study with structured and systematic stages through strict quality control. The results of the study show that multimedia developed is feasible to be produced and used in mathematics learning. Finally, the use of CAI through multimedia plays an important role in facilitating mathematical learning, especially in improving mathematical representation. However, the significance of differences in improving students' mathematical skill in representation ability is not found.