The present disclosure provides a copper nanoparticle paste suitable for high-precision direct-writing 3D printing, and preparation and application thereof. A triaryl phosphine compound or trialkyl phosphine compound is adopted as a copper powder protective agent, and copper nanoparticles are prepared into oil-soluble paste containing epoxy resin; and thus, the problem that the copper nanoparticle paste is prone to be oxidized in preparation and storage processes is solved, and the electrical conductivity of the copper nanoparticle paste is improved, to ensure that the copper nanoparticle paste is suitable for the high-precision direct-writing 3D printing.