Objective: To investigate the gender difference of left-behind adolescents mental health in rural junior middle schools, and to explore possible moderating role of parent-child interaction. Methods: Based on the data of China Education Panel Survey (CEPS) from 2014 to 2015, the self-reported parent-child interaction frequency and mental health of 3 470 eighth grade students lived in rural area were analyzed. Results: Mental health scores were higher in left-behind boys (68.90±22.45) whose parents migration compared to left-behind girls (63.59±20.83)(t=3.02, P<0.01). The two-level mixed effect linear regression model showed that the negative impact of parental migration on the parentchild interaction and mental health of left behind girls was greater than that of left behind boys (B=-0.90, -4.02, P<0.05). The frequency of parent-child interaction moderated the gender difference of mental health of left behind adolescents (P<0.01). The above-mentioned gender differences decreased after adding the frequency of parent-child interaction (B=-3.65, P<0.1). Conclusion The negative impact of parental migration on mental health of left-behind girls in junior high school is stronger than boys. It is needed to take more care of the mental health and promote parent-child communication for left-behind girls.