An　ultra-wideband　(UWB)　system　has　a　frequency　bandwidth　that　overlaps　with　spectra　of　many　existing　narrowband　radio　systems.　As　a　result,　impact　of　narrowband　interference　(NBI)　becomes　a　key　issue　in　the　development　of　UWB　systems.　In　this　paper,　under　the　IEEE802.15.4a　industrial　line-of-sight　(LOS)　channel　model,　the　effects　of　NBI　on　the　performance　of　the　recently　proposed　differential　code-shifted　reference　(DCSR)　UWB　systems　is　assessed　analytically　and　through　computer　simulations.　The　results　shows　that　DCSR　is　inherently　robustness　to　NBI　and　the　values　of　code　length　Nf,　as　well　as　transmission　code　number　M　play　an　important　role　in　mitigating　NBI.　Therefore,　shifting　and　detection　codes　need　to　be　carefully　designed　and　selected.　©　2010　IEEE.