The problem in this study is the lack of use of media in learning, the ability to understand concepts in learning is less effective, the lack of understanding in developing learning media. This study aims to determine the effectiveness of computer assisted tests based macromedia flash on the ability to understand concepts in PGSD students of Santo Thomas Catholic University. This research is using experimental research methods with quantitative approach. In field trials the average pretest score is 67. 03 while the average posttest score is 90. 14 with an average increase of 23. 11. The minimum gain value is 0. 70 with a high category while the maximum gain value is 1. 00. The results of data processing showed that the effectiveness of computer assisted tests on Macromedia Flash was 95. 00. It can be interpreted that the variable computer assisted test based on macromedia flash has a very positive effectiveness with a contribution of 95. 00 with very good criteria for the ability to understand the concept of students and 5. 00 others are influenced by other factors beyond the variable computer assisted test based macromedia flash.
