Gallium oxide (Ga₂O₃) materials possess excellent optoelectronic properties in the ultraviolet region and are widely used in blind detection. In this study, a metal-semiconductor-metal geometric model commonly used in Ga₂O₃ detectors is constructed based on the Monte Carlo method using the Geant4 software. The effects of Ga₂O₃ thickness and other parameters on the detection efficiency are analyzed. Based on the simulation results, a Ga₂O₃ ultraviolet detector prototype is designed, and experimental verification is conducted subsequently. The designed detector has a responsivity of 4.545 mA/W at zero bias voltage under 254 nm ultraviolet light with an intensity of 110 μW/cm², and a detection rate of 2.54×10¹² cm·Hz^1/2/W. These results indicate that the detector can effectively detect weak ultraviolet signals.