Positive Youth Development(PYD)is an integrative developmental theory that incorporates problem awareness,empirical evidence,and practical applications.PYD spans the entire developmental process,emphasizing the value of youth development from theoretical methods and principles to practical application.This study reviews the formation,background,and theoretical development of PYD,tracing its evolution from an ecological-situational orientation to a historical-cultural orientation over the past 30 years.Emphasizing the dialectical unity of history and logic,the study focuses on the philosophical and theoretical values of youth development mechanisms and practical approaches for promoting youth development.Drawing on historical context and practical experiences in China,this study explores the rich connotations and multiple implications of PYD.The PYD paradigm represents a significant theoretical shift in the field of youth development,reshaping research and practice,and advancing global study and policy processes.PYD moves beyond the"problem perspective"and"deficit model"by focusing on the strengths and potential of youth.It emphasizes the reciprocal interaction between the individual and the context,recognizing the dynamic interactions fundamental to youth development.As a comprehensive and systematic development theory,the core of PYD lies in the positive transformation of youth epistemology and the profound understanding of development mechanisms.The evolution of PYD from an ecological-situational orientation to a historical-cultural orientation expands our understanding of promoting positive youth development,research methods,and practical exploration.The core theoretical foundation of PYD's historical and cultural orientation is the relational developmental system(RDS),which integrates,expands,and deepens various developmental theories from ecological-situational orientations,such as ecological systems theory and developmental contextualism.RDS,as a cutting-edge theoretical framework in contemporary developmental science,emphasizes the complex dynamic mechanisms of various factors,spanning relationships from the micro-level of physiology,psychology,and behavior to the macro-level of society,culture,and history.It extends the research perspective of PYD to explore dynamic changes in the youth development process.In recent years,PYD research has extended to different regions and countries,focusing on youths in low-and middle-income countries,and revealing diverse developmental patterns.The integration of social and cultural factors has enhanced our understanding of PYD,providing a theoretical foundation and empirical evidence for promoting youth development programs and prevention work worldwide.Thus,the fundamental positive transformation in youth epistemology formed by PYD has multiple implications for exploring ways to study and promote positive development,tapping into youth potential,and formulating and implementing education policies in China.A comprehensive PYD research system has been established in Western countries.Based on the evolution and research experience of PYD worldwide,future PYD research should focus on cultural attributes and social realities in China,promoting the development and improvement of theoretical and applied systems of PYD.Therefore,it is necessary to integrate interdisciplinary research methods to systematically understand and effectively promote PYD development.Future research should consider the current status of youth development in China to integrate PYD into policies and practices,mobilize social resources,adopt a positive perspective toward youth,and promote their comprehensive and healthy growth.