Significance: High flux reactors are research reactors characterized by ultrahigh neutron flux levels (typically ranging from 10¹⁴ to 10¹⁵ n/(cm²·s) or higher). These devices primarily generate neutron irradiation for fundamental and applied research, including nuclear fuel and material irradiation testing, radioisotope production, and neutron science experimentation. They serve as critical irradiation testing platforms and fundamental research devices in nuclear science and technology, playing an indispensable role in industry, agriculture, and medical applications. This study systematically examined the technical attributes of high flux reactors and comprehensively reviewed China's achievements in high flux reactor design, technological development, and multipurpose utilization. Progress: Diverging from nuclear power reactor designs that focus on optimizing energy conversion efficiency and operational stability, high flux reactors aim to maximize neutron fluxes in irradiation channels, providing a technical foundation for fundamental and applied research while achieving optimal neutron economy. Key technical domains in high flux reactor development include reactor core configuration design, primary process system engineering, irradiation facility integration, and auxiliary system optimization. China's activities of high flux reactor development commenced in the 1960s, leading to landmark achievements, including the development of the High Flux Engineering Test Reactor, China Advanced Research Reactor, and China Mianyang Research Reactor. These facilities have achieved critical technological breakthroughs and diversified applications, contributing considerably to national nuclear energy advancement and socioeconomic development. The modern design philosophy of high flux reactors emphasizes advanced technology integration, functional versatility, and environmental sustainability. Design optimization focuses on enhancing reactor performance metrics while maintaining safety-economy balance and operational flexibility. Nevertheless, China's current high flux reactor designs show discernible limitations compared with international benchmarks, particularly in neutron flux intensity. For instance, the current maximum thermal neutron flux generated is ≤1.5×10¹⁵ n/(cm²·s), which limits the production of rare nuclides, such as ²⁵²Cf, ²⁴⁹Bk, and ²⁵³Es, through long transmutation chains and Pu/Am/Cm target irradiation. Further, insufficient irradiation testing capabilities in representative fast-neutron spectrums hinder the development and qualification of nuclear fuel and materials for Gen-IV advanced nuclear energy systems. Limitations are also observed in terms of irradiation capacity, auxiliary systems (e.g., deficiency in post-irradiation processing and radiochemical separation facilities), and application diversity. These limitations constrain the progress of strategic nuclear science and technology frontiers, including advanced nuclear material development, high-specific-activity radioisotope production, and cutting-edge neutron science research. Conclusions and Prospects: Strategic recommendations for China's high flux reactor development activities are proposed considering three aspects: innovation-driven technological upgrading to improve pivotal technical parameters and reactor performances, coordinated infrastructure planning to achieve the efficient utilization of irradiation resources, and open-resource sharing mechanisms to better drive the development of nuclear technology and related industries. Through technical upgrading and resource integration along with parallel research efforts in next-generation high flux reactor designs, which can substantially enhance technological sophistication and competitiveness, such initiatives are expected to provide robust support for nuclear energy innovation and nuclear technology advancement.