Microstructure of W-Cu alloy wire before and after hot-swaging was studied in this paper. Results show that a homogeneous microstructure of the W-Cu alloy wire was formed after hot-swaging treatment, and the tungsten particles were embedded in copper phases to form a networking structure; the W-Cu alloy wire has a microstructure of body-centered-cubic tungsten particles and face-centered-cubic copper phase, and did not change after hot-swaging. The intermediate phases have not been found during the process, but the size of the tungsten particles in the copper matrix becomes smaller. After hot-swaging, the treated W-Cu alloy wire has a relative density of 105.1%, and a conductivity of 47.2% IACS, the tensile and bending strength can be as large as 644 and 1600 MPa, respectively.