The vacuum system of the High Intensity heavy ion Accelerator Facility (HIAF) is critical for stable high-intensity beam transport and long-term reliable operation. This system, which spans 2 kilometers, faces numerous technical challenges. To reduce eddy current effects caused by rapidly changing magnetic fields, the Booster Ring (BRing) adopts an innovative titanium alloy-lined ultra-thin-walled (0.3 mm) vacuum chamber, combining 3D printing with Non-Evaporable Getter (NEG) coating technology. This chamber type constitutes 60% of the BRing. Through optimized outgassing processes and built-in component structures, an average pressure of 4.66 × $10^{-10}$ Pa was achieved, making it the world’s largest room-temperature ultra-thin-walled vacuum system. For the Spectrometer Ring (SRing) electron cooling system, limited installation space led to an integrated solution combining sputter ion pumps, built-in titanium wire evaporation, and NEG coating, achieving an average pressure of 1.02 × $10^{-9}$ Pa. In the high-radiation area of the High energy Fragment Separator (HFRS), a self-developed split sealing flange enables remote disassembly and reliable sealing, maintaining 2.5 × $10^{-6}$ Pa. Full integration was completed by September 2024, with all subsystems exceeding design specifications, providing a new engineering paradigm for future large-scale accelerator vacuum systems.