Online learning has a big influence on the learning process. The increase in learning outcomes in the era of the Covid-19 pandemic has poor results, this is due to the lack of activeness of argumentation in the classroom. This study aims to find out how the level of critical thinking ability of students uses e-learning learning. The type of research carried out is a descriptive study that only describes what is obtained or that occurs in a certain area that is observed. The courses in this study use the ongoing course, namely thermodynamics with a total of 20 participants. The instrument carried out in this study is a test of critical thinking skills in the form of description questions. Based on the results of data analysis, it shows an average pre test of 55.2 and an average post test of 79.6 while the average score of n-gain pre test and post test shows 0.54 with a moderate category, it can be concluded that e-learning learning can improve students' critical thinking skills.