Education is one of the things that become a benchmark in the quality of a nation. To answer the challenges of the times, the Ministry of Education and Culture for Research and Technology held an Independent Curriculum program to create fun learning so as to train students to think critically using the right methods. This research and development aims to produce critical thinking teaching materials  for students through STEM-based discovery learning. The material presented is rows and series of even semesters of class X. The method used is Research & Development by applying the ADDIE development model including, Analyze, Design, Development, Implementation, and Evaluation. The research subjects of class X students totaled 34 students. Products developed through validation stages from 2 material experts and 2 media experts to determine product feasibility, Products are tested on learning for effectiveness and reliability tests. The assessment results from material experts obtained a percentage of 82% for material expert preentase and 89% for the percentage of media experts with valid and worthy categories of use. The results of product effectiveness tests using SPSS version 26 showed that the significance level (GIS 2-tailed) was 0.00 ≤ 0.05. So it can be said that there is a significant difference between pretest and posttest scores.   The results of student reliability of the product showed a value of 0.907 > 0.60 with the questionnaire statement for the above variables being reliable and consistent.