We investigate the influence of source and drain bias voltages (VDS) on the quantum sub-band transport spectrum in the 10-nm width N-typed j unctionless nanowire transistor at the low temperature of 6 K.We demonstrate that the transverse electric field introduced from VDS has a minor influence on the threshold voltage of the device.The transverse electric field plays the role of amplifying the gate restriction effect of the channel.The one-dimensional (1D)-band dominated transport is demonstrated to be modulated by VDS in the saturation region and the linear region,with the sub-band energy levels in the channel (Echannel) intersecting with Fermi levels of the source (Efs) and the drain (EfD) in turn as Vg increases.The turning points from the linear region to the saturation region shift to higher gate voltages with VDS increase because the higher Fermi energy levels of the channel required to meet the situation of EfD =Echannel.We also find that the bias electric field has the effect to accelerate the thermally activated electrons in the channel,equivalent to the effect of thermal temperature on the increase of electron energy.Our work provides a detailed description of the bias-modulated quantum electronic properties,which will give a more comprehensive understanding of transport behavior in nanoscale devices.