This study aims to describe how the ability of students' understanding of concepts in solving algebra material problems according to Schemp theory. This study uses qualitative descriptive method. The data collection technique used is a test of the ability to understand algebraic concepts as many as 3 questions, interviews and observations. The data were analyzed based on 3 indicators of understanding the concept according to the scheme, namely being able to know and explain the method of solving the problem being done, being able to connect the method with various concepts and being able to adapt the method to new problems. The results showed that: 1) students with high categories are able to know and explain the method of solving the work done, able to connect the method with a variety of concepts even though the answers obtained are not precise and able to adjust the method to new problems; 2) students with the medium category are able to know and explain the method of completion is done, able to connect the method with a variety of concepts but the answers obtained are not appropriate, but not able to adjust the method to new problems; 3) students with low categories are able to know and explain the method of completion is done even though the answer is not right, in addition, students with low categories have not been able to connect the method with various concepts and have not been able to adjust the method to new problems.

Keywords: algebra; concept understanding ability; scheme theory.