Conventional semiconductor ultraviolet detectors have a wide wavelength response range. However, applications of ultraviolet light are generally highly sensitive to specific wavelength range, such as 320nm ultraviolet light is used in medical light therapy. Therefore, development of wavelength-selective ultraviolet detectors is of great significance. Using GaN-based p-i-n ultraviolet detectors with Ag-nanofilm as ohmic contact and wavelength-selective transmission layer, ultraviolet detector highly selective to the 320nm band ultraviolet light is successfully fabricated. The peak value of ultraviolet light transmittance with 70nm silver layer is higher than 30%. The dark current of the device at -5V is of the order of 10-12A. The peak responsivity of the device reaches 0.06A/W at 325nm, and the full width at half maximum is about 30nm.