This study was to develop and to suggest a lesson plan for the area of Human Development and Family Relationship in home economics for junior high school, based on Thelen s Group Investigation Model , Group investigation model by Thelen was developed from the theory that the education with special purpose such as societic knowledge is a method to lesson one s conflict. This study further developed from three main concepts : inquiry, knowledge and activities of learning group. This model can be used for any age and any subjects in order to solve the arised problems, rather than to accept pre-organized and pre-decided information. This study is organized around activities for seeking and practicing the rages of action to create dispersal home. First, one unit Understanding of Family was chosen that concerns and suitable for group investigation model Second, From the chosen chapter and problem were analyzed organized. Third, the chosen problem were re-analyzed, then a model lesson for group investigation was proposed.