The objective of this research is to discover the form of natural school culture in building character value of the students of Muhammadiyah Alam Surya Mentari Elementary School, Surakarta, Indonesia. This research is a case study using qualitative method. The technique of data collection is by using interview, observation, and documentation. The data is analyzed using flow model of analysis and using purposive sampling technique. The result of the research shows that the implementation of a fun and free natural school could build the students character, which reflected in the no-book rule, spider-web learning concept, and the characteristic monthly and yearly routine activities. The nature is the source of learning for the student; the students are independently trained in solving problem, and work in groups. The learning orientation with the students has a direct role through a fun concept based on the surrounding nature. The learning in natural school can support the life skill which could invite the student in exploring the knowledge and action which is useful for life outside school.
Key words: Natural school culture, alternative school, character