Junior high school is an important period for the development of teenagers, and it is also a key period for their moral development. Gratitude and cooperation. As two positive elements of psychological development, are essential to the formation of good character, sound personality, and individual socialization of middle school students. This study uses the method of tracking surveys and experiments to explore the effect of gratitude on the cooperation level of junior high school students. The first study explored the development characteristics of trait gratitude and cooperative tendency and the relationship between them.677 first-grade junior high school students in Suzhou were selected to carry out three follow-up surveys by using "gratitude questionnaire for Junior High School Students" and "Cooperation Tendency Questionnaire".The results showed the following: (1) The overall traits of gratitude and character orientation gratitude of girls are significantly higher than that of boys; (2)The overall level of cooperation tendency is high, and there is no significant difference in gender between the overall cooperation tendency and various dimensions of cooperation , but the difference is significant in time. T2's cooperation propensity level is significantly lower than T1 and T3's cooperation propensity levels; (3) The level of three times of trait gratitude and three times of cooperation tendency of junior high school students were significantly positively correlated with different test times. The trait gratitude of junior high school students can significantly and stably predict individual cooperative tendency. The second study explored the effect of state gratitude on cooperative behavior in the public goods dilemma. In this study, 112 students in a middle school in Shanghai were selected as the research subjects (64 in the experimental group and 48 in the control group). After measuring the initial level of trait gratitude using the junior high school students’ gratitude questionnaire, the subjects were randomly divided into two groups. The experimental group aroused state gratitude by reading gratitude stories and recalling gratitude experiences, and the control group aroused theirs by reading geographic expository text and recalling classroom layout. After taking the emotional manipulation test, each group of four participants conducted six rounds of simulation investment game experiment of the public goods dilemma paradigm. The results showed the following: (1) The level of gratitude and positive emotion in the experimental group was significantly higher than that in the control group, but there was no significant difference between the two groups；(2) The level of cooperative behavior in the simulation investment game in the experimental group was significantly higher than that in the control group; that is to say, the state gratitude of junior high school students can promote their cooperative behavior in the public goods dilemma. In other words, whether it is internal or external, the gratitude of junior high school students can play a positive role in promoting their cooperation level.