We present the systematic study of Vth and Idlin/ Idsat variability of nanowire transistors (NW Tr.) with various parameters (NW width (WNW) and height (HNW) down to 10nm, NW number (NNW), NW directions, channel dopants). By adopting NW circumference as Weff, the universal line appears in Pelgrom plot of both σVth and σId for a wide range of gate length (Lg), WNW and HNW. We found A vt reduction in NW Tr. compared to planar SOI Tr. due to gate grain alignment. Deviation of σVth and σIdlin of the narrowest Tr. from the universal line was eliminated by suppressing the parasitic resistance (RSD). σIdsat and σI dlin in NW Tr. can be reduced by improving the surface-roughness- limited mobility and its variations, respectively.