The purpose of this study was to determine the problems of mathematics in "thematic learning at the SD / MI level.This research uses a qualitative approach. The qualitative research design was carried out with a library research (library research) using various sources of literature as a source of research data. Sources of data in this study consist of secondary data and primary data. The data obtained were then analyzed descriptively which was presented systematically and objectively.The results of the study are students feeling bored, afraid when learning mathematics, the teacher still dominates in the learning process, the problems or problems conveyed by the teacher are still not contextual with the students' real life. Media, methods, strategies, and learning models applied by teachers do not pay attention to the characteristics of students. The thematic learning process of basic mathematics competence has not yet paid attention to the characteristics of mathematics learning, students have difficulty in understanding foreign symbols and languages. Solution to the problematics of mathematics in thematic learning, namely the teacher pays attention to 5 factors in the process of learning mathematics, namely personal, instructional, environmental, identity and socio-cultural factors. So the mathematical achievements of students can increase and have high-level thinking skills.