Transition-metal dichalcogenides (TMDCs) have been modified to show excellent electrocatalytic performance for the CO2 reduction reaction (CO2RR). However, little research has been reported on the edge modification of WS2 and its electrocatalytic CO2RR. In this work, the edge structure of WS2 with W atoms exposed in the top layer was established by density functional theory calculations. Through using WS2-xTM-y (x = 1, 2 or 3; y = 1 or 2; TM = Zn, Fe, Co or Ni) models by doping TM atoms on the top layer of WS2, the effects of dopant species, doping concentration and adsorption sites on their electrocatalytic activity were investigated. Among the models, the active site for the CO2RR is the W atoms. The doping of TM atoms would affect the bond strength between W and S atoms. After the doping of TM atoms in WS2-2TM-1 ones, the electrical conduction of S atoms and the underlying W atoms can greatly be improved. Thus the catalytic activities can be significantly increased, in which the WS2-2Zn-1 model shows the best catalytic activity. The limiting potential (UL) of the CO2RR to CO on the WS2-2Zn-1 model is -0.51 V and the Gibbs energy change (ΔG) for the adsorption of intermediates on the WS2-2Zn-1 model is ΔG(COOH*) = -0.37 and ΔG(CO*) = -0.51 eV, respectively. Solvation correction showed that WS2-2Zn-1 could maintain good catalytic performance in a wide range of pH values. The present results may provide a theoretical basis for the design and synthesis of novel electrocatalysts with high performance for the CO2RR.