This study explored the prevalence of anxiety and depressive symptoms among college students and analyzed the associations between only children and anxiety and depressive symptoms in college students in China. A total of 645 college students, from three universities in Jinan, Shandong, China, were investigated by questionnaire. The self-designed general information questionnaire was used to collect the demographic information such as gender, age, only children or not and so on. The Self-rating Anxiety Scale and Self-rating Depression Scale were used to reflect the psychological state of college students. Binary logistic regression analysis was applied to analyze associated factors of anxiety and depressive symptoms. We have found that there were 25.7% college students with anxiety symptom, 22.2% college students with depressive symptom, and 18.3% college students with a comorbidity of anxiety and depressive symptoms. The prevalence of anxiety symptom, depressive symptom, and comorbidity of anxiety and depressive symptoms in only children was higher than those among non-only children. There were no differences between males and females in anxiety symptom, depressive symptom, and comorbidity of anxiety and depressive symptoms among all college students, only child college students and non-only child college students. Only children were associated with anxiety symptom, depressive symptom, comorbidity of anxiety and depressive symptoms after adjusting potential important confounding factors, such as professional category, grade, parental relationship, parenting style, interpersonal relationship, activity participation enthusiasm, sleeping time, and eating habits. The prevalence of anxiety and depressive symptoms among college students was high. We should pay more attention to the mental health of college students, especially that of only child college students.