The electronic structure and transport properties of sawtooth penta-graphene nanoribbon (SSPGNR) are systematically studied via doping phosphorus and varying the dopant positions. First-principles calculations based on the density functional theory in combination with nonequilibrium Green's functions are utilized. It is found that the semiconducting-metallic phase transition occurs due to heavy doping. The electronic occupation at Fermi level correspondingly varies with the dopant sites. The most dispersing bands are observed for two doped SSPGNRs, which represents the noticeable carrier contribution to the current. Depending on the type of carbon hybridization (sp(3 )or sp(2)) at doping sites, the overall pictures for current of remaining ribbons are classified into three categories: fluctuation, parabola-like and Ohm-like. The huge difference revealed by doping arises from different coupling between phosphorus atoms and the neighboring sp3/sp2 hybridized carbon ones, which is indicated by various spatial Bloch-states distributions. Our finding offers abilities to alter electric current-voltage features in PGNR-based electronic devices.