This research was aimed to know : 1) the achievement of student’s comprehension ability of mathematic concept sho join assisted Cabri 3D discovery learning, 2) the achievement of comprehension ability who joined discovery learning, 3) the effect of assisted Cabri 3D discovery learning to mathematic concept comprehension, 4) the achievment of students learning interest who joined assisted Cabri 3D discovery learning, 5) the achievment of students learning interest who joined assisted discovery learning, 6) the effect of assisted Cabri 3D discovery learning to learnind interest. This research used posttest only control design. The research population in this research is all students of grade VIII in SMP Negeri 1 Kroya. The sample collection used cluster random sampling technique. The data research was got using test instrument of mathematic comprehension concept and using strudent’s interest questionnaire. The research result shows assisted Cabri 3D discovery learning affects the ability of concept comprehension and students learning interest.