Electron beam (e-beam) is one of the important tools in the field of nanotechnology. Here, the influence of e-beam irradiation on electron transport properties of monolayer WS2 field effect transistors was investigated by applying a gate voltage ( ${V} _{{\text {gs}}}$ ) during irradiation. The results indicate that high positive ${V} _{{\text {gs}}}$ during irradiation can dramatically increase electron doping in the WS2 sheets on dielectric substrate. After irradiation under positive ${V} _{{\text {gs}}}$ (10 V), the voltage threshold ( ${V} _{{\text {th}}}$ ) negatively shifts from 19 to −67.6 V and the field-effect mobility improves from 13.7 to 18.7 cm2 V−1 s−1 in comparison with that before irradiation. On contrary, high negative Vgs during irradiation tends to significantly reduce the doping level. In addition, relative high energy e-beam (e.g., 10 keV) irradiation under negative ${V} _{{\text {gs}}}$ is helpful for reducing the n-doping level. It is suggested that the charges trapped in the dielectric surface neighboring WS2 sheet dominate the transport properties after irradiation. This letter reveals that the ${V} _{{\text {gs}}}$ during e-beam irradiation is of critical importance for modifying electronic properties of atomically thin transition metal dichalcogenides.