The performances of UV-curable waterborne polyurethane-acrylate (WPUA) composite modified with nano calcium carbonate (NCA) were highlighted in this work. The γ-methacryloxy propyl trimethoxyl silane (KH-570) and polysorbate 80 (Tween-80) were used to enhance interfacial interaction between NCA and WPUA matrix. Transmission electron microscopy (TEM), particle size analysis and Fourier transfer infrared (FT-IR) spectrometry were employed to examine the micromorphology and the variation of function group of modified nano calcium carbonate (MNCA). Three different WPUA oligomers were investigated to obtain the optimized R value (the molar ratio of –NCO:–OH) via in situ polymerization and anion self-emulsification process. Results showed that WPUA displayed excellent film-forming ability and mechanical properties when R value was 2.2:1.0. These UV-curable WPUA films modified with MNCA (UV-MNCA/WPUA) were prepared through environmentally friendly UV-curable technology and investigated by thermogravimetric (TG) analysis, scanning electron microscope (SEM), X-ray diffractometer (XRD) and FT-IR. UV-MNCA/WPUA-3-3 film had the best overall performances with MNCA-2 and UV-WPUA at the mass ratio of 3.6%. Finally, the experimental results demonstrated that the as-obtained UV-curable coating had outstanding conservation effect to iron surface, providing a promising way for protection of iron cultural relics.