The purpose of this study was to understand the teacher's teaching behaviors by using TheDyadic Adaptation of the Cheffers' Adaptation of the Flanders' Interaction Analysis System( DAC ) . Take the physical education in special class for mental retardation of elementaryschool for example, the data were generated in the form of videotapes, and were analyzed byDAC to observe the interaction between the teacher and students. The results of this studywere summarized in the following sequence : 1 、 The express of teacher and students : The teacher mainly used verbal expression, andstudents used nonverbal expression instead. 2 、 the ratio of each interaction between the teacher and students : ( 1 ) The teacher's mainaction was to give direction 、 admire 、 ask questions @ provide messages 、 adapt student'sopinion. Criticism was seldom used. ( 2 ) Most behaviors students responded were expected. 3 、 the ratio of behavior of the teacher and individual student : Since the teacher usedone-by-one teaching, students' performance was quite the same. Interactions occurred mostfrequently with student Lie, and least frequently with student Liang. 4、 the property of the tool using : It is easier to use The Dyadic Adaptation of the Cheffers'Adaptation of the Flanders' Interaction Analysis System ( DAC ) to observe and analyze theinteractions between the teacher and students in special class for mental retardation physicaleducation.