Microstructure and properties of the Cu-5.2Ni-1.2Si and Cu-5.2Ni-1.5Al-1.2Si alloy were studied by optical microscope, Vickers hardness tester, two-arm electricity bridge, scanning electron microscope and transmission electron microscope. Results show that the developed dendrite appears in the casting ingot, which can be divided into dendrite area, non-equilibrium precipitates and the middle transition region. The dendrite area is rich in Cu element, the precipitates are rich in Ni and Si elements, and the Al element is distributed in the ingot evenly. After the appropriate thermo-mechanical treatment, the hardness of Cu-5.2Ni-1.5Al-1.2Si alloy is higher than that of Cu-5.2Ni-1.2Si alloy, and Ni2Si precipitates contribute to the main strength. Al element promotes the Ni2Si precipitation process. A new phase of Ni3Al is formed, which also improves the strength of the alloy effectively. Ordering transformation appears in the early state of ageing treatment, and the high strength is attributed to the precipitation particles. The designed alloy exhibits good anti-over aged capability