Introduction: Marriage is one of the most important events during an individual's life. Mental health as a component of personal characteristics, are associated with marital satisfaction. considering the role of mental health in a successful marriage, the impact of family health on community mental health, and major role of couples in this regard the present study aimed to determine the Mental health of people who are going to marry and its relation to some of their demographic factors in karaj 2012. Material and Methods: We performed a cross sectional study on the established group of 600 people who attended premarital assessment in a health center. They were selected by convenient sampling method. The data collection instrument was a demographic questionnaire and standardized Goldberge mental health (GHQ-28) questionnaire. The data was analyzed with SPSS/18 using descriptive and inferential statistical methods.(P<0.05) Findings: The mean score of mental health questionnaire was (16/2 ± 9/9). The results also showed that mental health and sex, religion, place of birth, marital history and employment status were significantly related (P<0.05) such that the mental health of men, Shea, born in the village, no history of marriage, and have a permanent job was higher. Conclusion: Recent research results indicate the desirability of mental health in 80.3 percent of in new couples.