Deep ultraviolet (deep-UV) spectroscopy has been proved to be a promising technique for in-situ and real-time nutrient measurement, where key components, such as deuterium lamp light source with wide wavelength range from 190nm to 400nm, has been deployed. For water with multi-contaminations, experimental results indicated that the luminescence emission excited by the wide band light source lead to considerable measurement error. It is desired to develop a narrowband multi-wavelength ultraviolet (UV) light source for a more accurate measurement. However, rare research has been done towards such functional devices, such as wavelength filters and switches, in deep-UV band. Therefore, a novel deep-UV narrow-band filter, based on the deep-UV transparent rectangular single-mode optical waveguide and arrayed waveguide grating (AWG) structure, is proposed and designed in this manuscript. In order to reduce the loss and crosstalk, we optimize the decoupling distance and the number of array waveguide. In conclusion, this deep-UV multiwavelength narrow band-pass filter is designed to be single-channel input and 7-channel output with central wavelengths from 210nm to 240nm, channel spacing of 5nm. This device has -3dB bandwidth of 1.87nm, inter-channel cross-talk of - 23.80dB, and insertion loss of -4.25dB, device size of 40 mm (length) x 10 mm (width) x 2mm (thickness), having integratable interface with waveguide type optical switches and detectors.