Objectives: The purpose of this study is to recognize the relation of menstrual pattern and dysmenorrhea affected by obesity of first-year female college students. Methods: From March 22th to April 2nd, 2010 we researched 251 first-year female students at OOcollege, aged 19(born after March 1991 to February 1992) by questionnaires to investigate their Body Mass Index(BMI), menstruation and dysmenorrhea. The BMI range of normal group is 18.5~25, abnormal group is over 25. Results: 1. The normal group was 227 people(90.4%) and the abnormal group(over BMI 25) was 24 people(9.6%). 2. In the mean of BMI, the normal group was $21.08{pm}1.64$ and the abnormal group was $27.94{pm}2.19$. 3. There was no statistical difference between the normal group and the abnormal group in menstrual cycle, menstrual amount, menstrual color and menstrual blood clot. 4. There was statistical difference between the normal group and the abnormal group in menarcheal age, menstrual duration and dysmenorrhea. 5. In the mean of VAS, the normal group was $3.68{pm}2.45$ and the abnormal group was $3.21{pm}2.05$, and two groups were not different statistically. Conclusion: This study showed the relation of menstrual pattern and dysmenorrhea affected by obesity. The normal group and the abnormal group were different statistically in menarcheal age, menstrual duration and dysmenorrhea. In consequence of this study, it was supposed that obesity had an effect on menstruation.