This study aims to determine how the skill of mathematical critical thinking of students with high achievement in grade X at SMK Negeri 1 Kawunganten, Academic Year 2019-2020 based on skill competencies. The is a descriptive-qualitative research. Purposive sampling was applied in this study, namely students with high achievement/ high category. The data collection techniques used were written tests, interviews, and documentation. This study uses triangulation techniques in analyzing test results and interviews. There are 4 indicators of critical thinking used as benchmarks, namely: Interpretation, Analysis, Inference, and Evaluation. It is concluded that students with high achievement/high category of TBSM skill competency are able to meet all indicators of mathematical critical thinking critical thinking, namely Interpretation, Analysis, Inference, and Evaluation. Students with high achievement in the TKRO expertise competency are not all able to meet all indicators of mathematical critical thinking namely Inference indicators. Not all students with high achievement/high category of multimedia expertise are able to meet all the indicators of mathematical critical thinking namely Inference indicators. Students with high achievement/high category in the animation skill competency are not able to meet all the indicators of mathematical critical thinking namely Inference indicators.