As candidates for conductors used in high-field extreme conditions, Cu-Ag in-situ composites are required to possess high strength and conductivity; however, most Cu-Ag in-situ composites do not possess both characteristics. Therefore, it is important to determine the appropriate composition design of Cu-Ag composites that can enhance the mechanical properties while maintaining a relatively good electrical conductivity. This paper describes the effect of several potential alloying elements (Cr, Nb, and Zr) on the microstructures and mechanical properties of Cu-6 pctAg in-situ composites. The results reveal that the addition of both Cr and Nb refined the morphology of the Ag filaments and considerably improved the tensile strengths of the drawn Cu-Ag composites at large strains. Particularly, the ultimate tensile strengths of the Cu-6 pctAg-1 pctCr composites were improved by approximately 23 pct than that of the Cu-6 pctAg binary composites, with only a slight loss in conductivity. By contrast, the addition of 1 pctZr to the Cu-Ag composites had a negative effect on the morphology of the Ag filaments; it only improved the hardness at low drawing stains while reducing both the tensile strength and electrical conductivity.