Objectives This study focused on the interaction between teachers and students among the various characteristics of project based learning, and attempted to reveal the characteristics by observing project-based elementary school classes. Methods To this end, The AF analysis was used to analyze the language interaction between teachers and students, and the CLASS analysis was used to analyze the ‘emotional support, classroom organization, and instructional support’ interaction between teachers and students. In addition, Pearson's correlation analysis was conducted to confirm the correlation between the Flanders area analysis, the Flanders Top 10 Index, and the CLASS analysis. In addition, Classes were classified by type to confirm the results of the interaction analysis of ‘emotional support, classroom organization, and instructional support’ according to the type of language interaction, and the results were compared. Results First, In the project based learning, the ratio of items 0 (others) was the highest, followed by items 5 (lecture), items 9 (student-led remarks), and items 4 (teacher's questions). Second, In the project based learning, the index in which teachers accept students' opinions or emotions and the index in which students take the initiative in asking and speaking were high. In addition, the index of teachers asking questions using students' remarks was also high. On the other hand, In the project based learning, the index in which teachers criticize students or justify teachers' authority was low. Third, In the project based learning, the flow of ‘teacher's lecture-nonverbal situation-teacher's lecture’ was high. Fourth, In the project based learning, the ‘emotional support’ area was the highest, followed by the ‘classroom organization’ and ‘instructional support’ area. However, the average for all three areas showed a moderate or higher level, and the deviation was not large, showing a similar tendency. Conclusions First, Project based learning is a class that utilize directive remarks from teachers to induce student-led inquiry activities. Second, Project based learning is a class that emphasizes the attitude of warm-hearted acceptance of students' opinions or emotions without advocating the authority of teachers. Third, Project based learning is a class with a high percentage of students leading throughout the class. Fourth, Project based learning is a class that mainly utilize teachers' questions as feedback on students' remarks. Fifth, Project based learning is a class in which non-verbal situations such as student-led inquiry activities or waiting time for student to think account for a high percentage. Sixth, The flow of project based learning is at a very high rate of ‘teacher's lectures-nonverbal situations-teacher's lectures’. Seventh, Project based learning is a class in which interactions through ‘emotional support, classroom organization, and instructional support’ appear positively.