This study discusses the analysis of students' critical thinking skills profile and the implementation of PBL on heat material. This study aimed to determine the profile of students' critical thinking skills and the implementation of PBL on heat material at SMAN 1 Gondang. This study used pre-research with qualitative descriptive analysis with a sample of 91 SMA Negeri 1 Gondang students. Data collection techniques were written tests, student response questionnaires, and teacher interviews. The study found that students critical thinking skills were in a low category, and inference was the indicator of essential thinking skills with the lowest average. Teachers still used lecture methods and conventional teaching materials during learning, so it was necessary to apply a model, namely a problem-based learning model assisted by a 3D module, which was expected to improve critical thinking skills on heat material. Learning innovations need to be carried out to improve students' critical thinking skills, especially in physics learning, one of which is the application of Problem-Based Learning assisted by a 3D module.