The aim of The present study investigated the extent of social belonging of people of Mashhad to Iran society and the relationship with social trust and individualism has been. Research has been Survey and data was collected through questionnaires. The Statistical Society' who was twenty years in Mashhad with a population 1530827 equals the number 384 as the sample size by using multi-stage cluster sampling is the selection and Specified. The results show the average amount of social belonging, respondents scored2/7, and to a maximum of5 points, the value of 2/3 is the score. The social belonging of the people of Mashhad to Iran is in the middle. Social belonging with increasing age and also social belonging in the Persians than other ethnic groups as well as practitioners than other people and in The middle class than other classes more have been. Overall, the independent variables were entered into multiple regression coefficients with 40% of the changes made to explain the dependent variable (R2=0/40) the variable «social trust» by a factor of 0/61 had the greatest impact on social belonging and then « extreme individualism «-0/1 8 determining factor influencing the next time it is used, thus increasing social distrust of the people most affected has had on their social belonging.