Abstract: Physical Activity (PA) and health promotion of children and adolescents has long been a important theme in global sports sciences and public health practices. With the deepening of the understanding of the total development of mankind in recent years, the important health concept, Motor Competence (MC) has been led to the complete research areas of children and adolescents' PA and health promotion. The present study expounds the relationships between MC, PA, health-related fitness (HRF) , perceived competence (PC) and weight status (WS) , analyzes the significance of MC on children and adolescents' PA and health promotion based on MC research models of children and adolescents which have been established by foreign scholars. The research prospects of further studies are 1) Inventing advancing MC instruments;2) exploring the specific influences of MC on PA;3) investigating the positive effects of developing MC on cognition and academic performance. Suggestions:Physical educators and researchers should exert scientific intervention on children and adolescents' MC, make them participate in PA actively and promote the comprehensive development of physical and mental health.