||The development of VOCs gas sensor has been studying in many application fields such as environmental monitoring, industrial safety and healthcare since VOCs could induce health problems, indoor air pollution and environmental damage. In this talk, I would like to introduce the noble metal catalytic effect on the performance of MOS gas sensor. Ag nanoparticles are decorated on high resolution CuO nanopattern by using e-beam evaporation. Ag additives on CuO pattern (30nm width, 400 nm height) showed the ultrahigh sensitivity toward to VOCs (toluene, ammonia, ethanol, propanal and acetone) due to its unique morphological and catalytic effects. Moreover, it exhibited about two times higher gas response over a wide range of acetone concentration (125 ppb to 1000 ppm) compared with the pristine CuO nanopattern.