Conceptual understanding and physics learning process are related to each other. Conceptual understanding makes students able to transform knowledge into multiple representations and application in daily life. The aim of this research is to analyse students' conceptual understanding of heat and temperature by applying instrument Two-tier Multiple Choice (TTMC). This research is a descriptive research with subjects of the research are students of 10th grade in Surakarta in the academic year of 2016/2017 that represents the school with a high, medium and low category. Before instrument TTMC tested to sample, instrument validated by an expert. The instrument TTMC has good content validity between 0.89 -1, the reliability of the first tier is 0.82, the second tier is 0.70, difficulty index is a medium category, and distractor index has good function. Based on the data and analysis, most of students in high, medium and low categorized school have low concept understanding in temperature and expansion, in other concepts (heat, Black principle and heat transfer) they have adequate understanding. From this research, teachers know the students" concept understanding, so teachers can choose the suitable learning method in physics learning activities and teachers can develop and apply two-tier multiple choice as alternative instrument to measure students" conceptual understanding.