A compound additive, gelatin (G) + sodium dodecyl sulfate (SDS), was firstly proposed to synthesize nanotwinned Cu with enhanced mechanical properties and electrical conductivity by direct current (DC) electrodeposition. The effect of compound additive in acid copper plating electrolyte on microstructure, nanoindentation hardness, tensile properties and electrical conductivity of electrodeposited copper was investigated. The optimum conditions of DC electrodeposition and deposition rate of electrodeposited copper were evaluated. The results show that the formation of nanotwins and the refinement of grains were enhanced after adding the 20 mg/L SDS + 15 mg/L G of compound additive, in return, which has a positive contribution to the enhanced mechanical properties and electrical conductivity. Tensile strength, hardness and the elongation to failure of electrodeposited Cu were 490 MPa, 1.79 GPa and 7.1%, respectively. The electrical conductivity was 97.4% IACS at room temperature. The enhancement mechanism of tensile properties and electrical conductivity was explained in view of high density of nanotwins.