Nowadays, with the rapid development of electronic information technology, solar-blind ultraviolet (UV) detectors having large anti-interference ability and higher sensitivity are attracting much attention. Possessing ultra-wide band gap, high optical absorption coefficient, good thermal conductivity, and high breakdown field strength, hexagonal boron nitride (h-BN) has become a promising material for solar-blind UV detectors. Additionally, high mechanical strength and optical transparency of h-BN make it a potential candidate for flexible detector. However, the h-BN films prepared at low temperatures often contain many defects, which greatly limit their performance as a detector. In this work, high-quality h-BN films were prepared on sapphire and Si substrates using B as growth source at room temperature by reactive magnetron sputtering method, and then a high-performance solar-blind UV detector was fabricated based on h-BN films. The prepared h-BN solar-blind UV detector has extremely low dark current (0.07 pA), high responsivity (1.37 μA/W) and detectivity (2.73×1010 Jones) at 3 V. These results indicate that preparation of high-quality h-BN film and its solar-blind UV detector at room temperature are feasible. The study also provides a reference for the application of h-BN detector working at room temperature.