This study departs from the unequal distribution of student learning outcomes in thematic learning as espoused in the old paradigm of learning. Students who stand out in academics will be more prominent and students who did not stand out in academics increasingly drowned. Appropriate rationale, it is necessary solutions to overcome them. The solution is a cooperative learning type GI. And the purpose of this research is to examine the activities of teachers and students in thematic learning achievement using cooperative learning model type group investigation and assess student achievement results in thematic learning before and after the implement cooperative learning model type investigation group (GI). Thematic is perfected in learning for learning at the school level, that contribute to the functioning of the social sciences that are teoritif in real life in the community. Type of cooperative learning model G1 is a group cooperative learning model heterogeneous 5-6 students by considering students' familiarity and interest, then the investigation formulate and agree on the division of labor to handle the investigation of concepts that have formulated a method of learning. Subjects in this study were second grade students of SDN lebani Suko totaling 30 students. The results of student achievement has increased for 2 cycles of learning, with the percentage of completeness 53.33% in cycle I, 86.66% in cycle II. From the results it can be concluded that cooperative learning model type G1 can improve student learning outcomes in grade 2 thematic learning.