The purpose of this study was to describe students' mistakes in solving word problems based on the Watson Criteria. The material used in this study was a two-variable linear equation system (SPLDV) and was implemented at SMP Negeri 1 Kembaran. The type of this research was a qualitative description. The subjects of this study were students of class VIII F who were selected through a purposive sampling technique. Students were grouped into three groups, namely groups of students with high, medium, and low learning achievement in which three students were selected from each group. The data in this study were collected using written tests and interviews. Meanwhile, the data validation test used technical triangulation by comparing the results of written tests and interviews. The results of this study showed that 1) high learning achievement students made mistakes in the response level conflict stage, omitted conclusions, omitted data, and indirect manipulation; 2) student with medium learning achievement made mistakes at the stage of the problem of skill hierarchy, level conflict response, omitted conclusions, omitted data, and indirect manipulation; and 3) students with low learning achievement made mistakes at the stage of incorrect data, skill hierarchy problems, inappropriate procedures, level conflicts response, omitted conclusions, omitted data, and indirect manipulation.