This study aimed to measure the effectiveness of the Discovery-based Multiple Representation (DMR) learning model that use to improve student critical thinking skills (CTS) of students on environmental change material. This study used the pre-experiment method, with a one-group pretest-posttest design. The populace of this study was students in MTs 2 Sleman. The sample was selected by a random sampling technique amounting to 60 people. The instrument used to collect data on critical thinking capability was an essay test to measure the effectiveness of the DMR learning model in increasing students' CTS. The data analysis technique used paired sample t-test with (p=0.05) to test the effectiveness of the DMR learning model. The results showed that the DMR learning model increased student CTS significantly in natural science learning. The normalized gain value of 0.25 indicates the enhancement of student CTS at the middle category. Thus, the DMR learning model is useful as an alternative to improve students' CTS on environmental change topics. [Note: The page range (927-944) shown on the PDF is incorrect. The correct page range is 927-945.]