This paper describes research based on observational data of junior high school students' discussion processes in small group contexts solving problem. Using Mercer's models of three distinctive social modes of thinking, or disputational talk, cumulative talk and exploratory talk, we analyzed and interpreted discourse data of students from 7th grade to 9th. As the results, we see most students in all grades often discussing in the way of cumulative talk. We also see the exploratory talk, which helps group to solve problem, in 7th and 8th grade students' discussion.