By using a combined method of density functional theory and non-equilibrium Green's function formalism,we investigate the electronic transport properties of carbon-doped armchair phosphorene nanoribbons (APNRs).The results show that C atom doping can strongly affect the electronic transport properties of the APNR and change it from semiconductor to metal.Meanwhile,obvious negative differential resistance (NDR) behaviors are obtained by tuning the doping position and concentration.In particular,with reducing doping concentration,NDR peak position can enter into mV bias range.These results provide a theoretical support to design the related nanodevice by tuning the doping position and concentration in the APNRs.