Abstract: To reduce costs and improve environmental performance, water-based carrier was used to replace organic carrier. The copper powders mixed with particle diameters of 5 μm and 15 μm were used as main conductive phase, and a small amount of graphene is added as conductive reinforcement phase. The water-based graphene-copper composite conductive paste was prepared according to a certain mass ratio. The effects of water-based carrier on paste performance were studied by four-probe tester and scanning electron microscope (SEM), and the conductive connection model was established by analysing for electric conduction mechanism. The results show that: when the mass ratio of deionized water: cmc: peg: defoamer is 96.9:1.5:1.5:0.1, the water-based carrier has better performance. When the water-based carrier content is 30%, the prepared water-based graphene-copper composite conductive paste has excellent printing performance and a small electrical resistivity of 1.65 mΩ?cm. The resistivity of water-based composite paste with graphene is 95.1% lower than that of copper paste and 75.78% lower than that of graphene-copper composite paste prepared by organic carrier. The conductive film is flatter and denser, and the contact between conductive phases is closer. A large number of graphene overlaps or fills the gap between copper powders laterally or radially, forming conductive channels in parallel or in series with copper powders. A dense conductive network is formed and the conductivity of the composite pastes can be improved.