Novel ultrahigh strength Ni2Sistrengthened brasses were fabricated, and microstructure and properties were investigatedusing scanning electron microscopy, optical microscopy, transmission electron microscopy, X-ray diffraction analysis, hardnessmeasurement, and electrical conductivity test. After optimal treatments (solid solution treated at 900 ℃ for 2 h, hotrolledby 80%, cold-rolled by 80%, and ageing treated at 300 ℃ for 8 h), the Cu-20Zn-3Ni-0.68Si alloy’s hardness, tensilestrength, yield strength, and electrical conductivity is 270.6 HV, 964 MPa, 933 MPa, 21.6%IACS, and 3.4%, respectively. δ-Ni2Si precipitates formed during the annealing process, which had a crystal orientation relationship with the matrix: (001)m// (001) δ, and [110]m// [100]δ. Quasi-cleavage fracture surfaces with shallow dimples were presented in both the Cu-20Zn-1.5Ni-0.34Si and the Cu-20Zn-3Ni-0.68Si alloy. These findings give a new method to develop new high strength low-costbrass copper materials.