The hot deformation behavior of Cu-bearing 304L stainless steel was studied by performing hot compression on Gleeble-3800 thermo mechanical simulator in the temperatures of 900~1150 ℃ and strain rates of 0.01~20 s^-1, and the processing maps were established by stress-strain curves. Results show that the better processing temperature range is narrowed from 200 °C to 75 °C with the increase of copper content in the alloy (0wt%Cu-304L, 2.42wt%Cu-304L, 3.60wt%Cu-304L). The alloy microstructure characteri-zation reveals that the main causes of instability are local flow instability, shear zone, void and cracking. At the same time, it is found that the plastic deformation can be converted into heat in a short time, leading to the local temperature rise of the deformed materials, which makes the copper segregation area with relatively low melting point easy to form holes and to become the source of cracking, and then reduces the hot workability.