Density-functional theory in combination with the non-equilibrium Green’s function formalism is used to study the effect of silicon doping and phosphorus passivation on the electronic transport properties of zigzag graphene nanoribbons (ZGNRs). We study the edge structures passivated by H atoms and by P atoms. In this work, Si atoms are used to substitute C atoms located at the edge of the samples. We consider ZGNRs terminated by H and P atoms with four zigzag carbon chains (4-ZGNRs) in case of six various configurations. Our calculated results determine that the Si doping improves significantly the current of samples by the number of dopants. Moreover, there is dramatical difference in the transmission spectrum of P-passivated ZGNRs and Hpassivated ZGNRs i.e. P passivation not only destroys an enhanced transmission at the Fermi level, which is typical for graphene nanoribbons, but also increases considerably the intensity of transmission spectrum with ballistic transport properties. Furthermore, the numerical results illustrate that pristine H-terminated samples have a broadening band gap in transmission spectra when the bias voltage increases. The relationship between the outcomes indicates that such silicon doping and phosphorus passivation are effective and providing a promising way to modulate the properties of ZGNRs for nanoelectronic device applications.