Introduction: The interactions of girl and boy before marriage are one of our current society complex phenomenons that are constantly controlled and limited and it is influenced by culture , religion, and customs of the society . Social-psychological Factors and needs are caused of such relationships. Purpose of this paper is to identify the influencing factors of this phenomenon.

  Method : The present study has been conducted by survey . The samples are based on the Cochran formula 240 students of Yazd University Who were selected by relative stratified sampling. Data was collected through researcher questionnaire was made, then date was analyzed by the SPSS software and the results achieved by using test t, correlation and regression .

  Findings: The findings show that more than 60% of respondents have positive attitudes towards marriage relationships before marriage, although , 22/5 % of respondents don’t have relations with the opposite sex . Also , 36/7 percent of respondents have relations with one person and 27 percent of them experienced with more than one person.

  Conclusion: The Tendency to before marriage relations has had positive relation with family income and father 's education and person age and negative relation with levels of religiosity , good relations with parents and the average of the University. Although, there wasn't a significant correlation with income , education , and average . Also , regression explain ed that approximately explain variables two emotional need and religious 27% of changes of tendency to before marriage relation .