Offshore oil spills can cause serious environmental damage. Timely and accurate detection and identification are crucial for controlling oil spills. Solar-blind ultraviolet (UV) monitoring for oil spills is less affected by solar background radiation, which can improve the accuracy of oil spill monitoring. A reflection spectroscopy test system was designed and constructed to measure the reflectance spectra of four types of simulated marine oil spills (-20# Diesel, -35# Diesel, 95# Gasoline, and Light crude oil) in the solar-blind UV, medium-wavelength UV, and long-wavelength UV bands. The variation trend of reflectance with film thickness was analyzed. Meanwhile, the reflectivity of oil films with different thicknesses was simulated and calculated using the single-layer feature matrix at different wavelengths. The experimental and simulation results showed that refined oil and crude oil have higher reflectivity than seawater in the UV band, and the reflectivity oscillates periodically with changes in the oil film thickness and eventually approaches the reflectivity of pure oil. The period and reflectivity peak is mainly determined by the oils complex refractive index and the oil films thickness, and the experimental and numerical simulation results are consistent. This research shows that in the solar-blind UV band, the range of reflectance oscillations with oil film thickness is smaller, and oil films have higher discrimin ability from the water background. Therefore, using active solar-blind UV reflection spectroscopy to detect oil spills can reduce the interference of solar background radiation and provide the possibility for all-day and all-weather monitoring of oil spill targets.