Introduction: This research to study of effect of group investigation method on the development of students social skills.Methods: In this study, using a quasi-experimental by pretest-posttest design with control and experimental groups was performed. The experimental group was taught by group investigation method and the control group did not receive variable.The population, was the junior high school girl students in 6 area of Mashhad. Among them, 51 people were selected random cluster sampling as participants and then 26 people randomly placed in the experimental group and 25 people in the control group and answered to a questionnaire of Matson, Ratatori and Helsel's social skills. by using Cronbach's alpha, The reliability of the test was obtained in the pre-test 0/79 and post-test 0.95.Results: The data collected with the aid of descriptive statistics and multivariate analysis of covariance were analyzed. Results showed that the experimental and control groups in the pre-test is not much different, but in the test, the average was higher than the control group, the experimental group and the control pre-test score, the scores of social skills development was a significant difference between control and experimental groups (P>0.001).Conclusion: According to findings of this study can be concluded that, general, teaching by using group group investigation method influenced on social skills development of students and components of appropriate social skills, anti-social behavior, aggression and impulsiveness, domination and self-confidence and relationship to peer influence and This component has been improved. Therefore, This study suggests that using social models such as group investigation teaching method to improve social skills.