Mastery of concepts is one of the important things in learning science in the 21st century. Various innovations are carried out to motivate and make science learning attractive to students. Among the difficulties in learning science are the many abstract concepts. Abstract concepts need to be visualized so that students are easily understood. The combination of innovative learning models with computer simulations is needed to get better learning outcomes. The purpose of this study was to examine the effectiveness of project-based learning models assisted by computer simulations of mastering the concept of prospective science teachers. This study involved three groups given treatment with project-based learning assisted by computer simulation. Mastery of concepts is measured using tests. The results of the study showed an increase in mastery of the concept of prospective teachers in the scientific concepts learned. The use of computer simulations has been proven to help participants visualize concepts so that they are easy to understand.