Doping with foreign metals is one of the important methods to enhance CO2 reduction performance of monometallic catalysts. Doping content plays a significant role in the activity and selectivity of catalysts. Herein, a study of density functional theory (DFT) calculation was carried out to investigate the effects of Pd doping content on CO2 reduction selectivity and activity of Pd@Cu catalysts. The results indicated that the overpotential of CO2 reduction to HCOOH increases with the rise of Pd doping content while the overpotential of CO production decreases. Mulliken charge and d-band center of the atom corresponding to the active site increase with the raise of Pd doping content. Pd@Cu with the highest Pd doping content exhibits good catalytic activity for CO production. Its overpotential required for CO production is lower than that of the many catalysts reported. Pd@Cu with the lowest Pd doping content is a promising catalyst to produce HCOOH, only a lower overpotential of 0.167 V is required to enable CO2 reduction to HCOOH. This work demonstrates the critical role of Pd doping content on the CO2RR product selectivity of Pd@Cu electrocatalysts, and may pave a new way to design catalysts with high activity and selectivity toward a single product in CO2RR conversion.