Based on the non-equilibrium Green function-density functional theory, the photoelectric effect of doped monolayer WS2 with VA group elements (N, P, As or Sb) was calculated by first-principles, and the microcosmic mechanism of doping to improve the photogalvanic effect was explained. The results show that photocurrent can be generated in the monolayer WS2 under linearly polarized light. Since the doping reduces the spatial inversion symmetry of the monolayer WS2, the photocurrent generated by the illuminated central area of the monolayer WS2 doped with N, P, As, or Sb significantly increases, and the photocurrent and the polarization angle show a perfect sinusoidal relationship, which conforms to the phenomenological theory. Among them, the effect of N doping is the best. The doped monolayer WS2 obtains the maximum photocurrent (1.75) when the photon energy is 3.1 eV, and the polarization sensitivity reaches the maximum (18.1). The monolayer WS2 doped with P, As and Sb achieves a larger photocurrent when the photon energy is 3.9 eV, and has a higher polarization sensitivity. The research results show that the doping can effectively enhance the photogalvanic effect and obtain higher polarization sensitivity, revealing the potential application prospects of doped monolayer.