The purpose of holding this classroom action research is: To find out how to increase understanding of science learning through the application of the demonstration method for Class V.A students of SD Negeri Mataram Model Odd Semester 2019/2020 Academic Year. The method used in data collection in this research is the method of giving tests, interviews, observations, field notes, and documentation. This type of research is the PTK. The results of this study were the use of demonstration methods in science learning on the subject of human and animal organs to improve students' understanding of this subject. Students' understanding of science learning increases with the application of demonstration methods to increase understanding of science learning. This is evidenced by the results of the evaluation in the pre-cycle only 65.00% who completed or more than the KKM, namely 75, increased with 80.00% learning completeness in cycle I and became 100% in cycle II classical student learning completeness had been achieved.