This research aimed at describing the effectiveness of the macromedia flash based inquiry learning in improving students' concept understanding in chemistry learning. It was an experimental research with post-test only design. The population was the eleventh-grade science students of state high school 5 Yogyakarta, Indonesia. The sample in this research was taken by random sampling technique as many as two groups, namely the experimental group and control group. The students in the experimental group learned through the macromedia flash based inquiry learning, while students in the control group learned through the conventional learning. The data on the students' concept understanding were collected through the concept understanding test. The data were analyzed by using one-way ANOVA with SPSS version 23.0. The results showed that students who used macromedia flash based inquiry learning in the assessment process have increased concept understanding better than those used conventional learning (value of significant < 0.05).