Objective To explore the influencing factors of the transition to adults on children with cancer from the perspective of professional care providers,so as to improve their transition readiness. Methods From September 2020 to June 2021,by phenomenological research methods,semi-structured in-depth interviews were conducted with 5 doctors,19 nurses and 3 social workers. The interview data were transcribed,coded,analyzed and refined. Results From the perspective of professional care providers,the factors influencing the transition of children with cancer can be summarized into 4 factors,i.e. individual,family,medical system and society,and 9 sub-factors,i.e. diagnosis and treatment experience,disease cognition,autonomy,transitional consciousness,education style,professional team,profes-sional service,social environment and service system. Conclusion There are multiple factors influencing the transition to adulthood. To assist them to effectively cope with the long-term impact of disease and treatment,it is necessary to raise the public attention,encourage children to be informed and participate in disease management,upgrade professionals’ capabilities,strengthen the continuity of long-term follow-up,develop the service system,and develop individualized and targeted intervention adapted to Chinese situations.