Localized surface plasmon resonance (LSPR) provides an effective approach to further improve the performance of photodetectors. In this work, we introduce the Al nanoparticles (Al-NPs) on the surface of β-Ga₂O₃ thin film by rapid thermal annealing in order to improve the performance of β-Ga₂O₃ solar-blind ultraviolet photodetectors Al nanoparticles arrays, which can not only decrease the dark current but also enhance the responsivity and specific detectivity. As a result, the responsivity of β-Ga₂O₃-based metal-semiconductor-metal (MSM) solar-blind ultraviolet photodetectors with Al-NPs can reach 2.7 A/W, and the specific detectivity can reach 1.35′1014 cm×Hz^1/2×W^-1 under the 254 nm radiation and 10 V bias. Both parameters are more than 1.5 times and 2 times higher than those without Al nanoparticles, respectively.