Medical mutual aid is an important component of multi-level medical security system. West China Second University Hospital of Sichuan University led the establishment of the pediatric specialty alliance " West China Women and Children Alliance". Based on customized and inclusive mutual insurance product " Family Doctor Mutual Aid Plan", the alliance implemented key links such as mutual aid product forms, patient risk protection, institutional financing and hematopoiesis, and distribution of benefits to all parties, explored innovative mutual aid funding, payment, and incentive mechanisms, forming a closed-loop pediatric tiered diagnosis and treatment service system with the Mutual Aid Plan as the core. This system operated continuously under the " Four-in-One" framework, stimulating the integration of medical insurance and service supply systems while enhancing the synergistic effect between mutual insurance and social security. It has formed a distinctive health-centered multi-level medical security system within the alliance, and could provide reference for the construction and exploration of hierarchical diagnosis and treatment system.