Printed electronics is one of the inexpensive fabrication for electronic circuits and it is expected to be an alternative to conventional method such as photolithography. Commercial conductive ink for printed electronics often uses Ag nanoparticles(AgNPs), but AgNPs are expensive. Accordingly, Cu nanoparticles(CuNPs) are expected to replace for AgNPs, because Copper is much cheaper than silver and has high conductivity. However, Copper oxidises easily in the atmosphere. To prevent oxidation of Cu, organic compounds have been used as coverings for CuNPs, but these non-metallic coverings often reduce conductivity of CuNPs. Hence, Cu-Ag nanocomposites(Cu-Ag NC) have been considered as an alternative method to prevent Cu oxidation. In this study, Cu-Ag NC were easily synthesized under high concentration condition with microwaves and ultrasonication. Microwave heating is effective method for synthesis of nanoparticles because of its effect to heat polar solvents quickly and uniformly. Ultrasonication is easily process to synthesize composites of nanoparticles and other materials. The sample synthesized showed the form that AgNPs attached to the surface of CuNPs in its SEM images. Thermogravimetry measurement suggested that the sample has high oxidation resistance against CuNPs.