Feng, G.Y. JACoW Publishing Geneva, Switzerland Electron beam emittance of storage rings can be reduced to very small values by using muti-bend achromat (MBA) lattice, for this reason, fourth-generation of storage ring light sources are emerging to push beyond the brightness and coherence reached by third-generation light sources. Hefei Advanced Light Facility (HALF) project was put forward a few years ago as a fourth-generation light source with soft X-ray diffraction-limited storage ring operated at 2.2 GeV. A 2.2 GeV linear accelerator will be used as a full-energy injector for the storage ring. The ring with circumference of 480 m employs an MBA lattice to achieve a bare lattice emittance of 85 pm·rad. The engineering implementation of the MBA lattice ring raises several technological issues, for example, high field gradient magnet, low-conductance vacuum chamber with small aperture and with non-evaporable getter (NEG) coating, high beam injection efficiency with small dynamic aperture, etc. For responding to these challenges, a preliminary research and development project of HALF was completed at the end of 2020. Some details of HALF conceptual design, key technologies and plans are presented.