To improve the antibacterial properties of 304L austenitic stainless steel, copper is often added as an antibacterial agent, but the forming performance of the resulting material is poor, impacting its actual production and use. Therefore, this study investigated the influence of copper addition on the formability of 304L austenitic stainless steel with drawing, cupping and conical cup forming tests. Mechanical properties were determined with tensile and hardness tests. The microstructure and phase transformation were further characterized by metallographic microscopy, scanning electron microscopy and x-ray diffraction analysis. It was found that the addition of copper impaired the mechanical properties of 304L austenitic stainless steel, increased the stacking fault energy of the material and inhibited the occurrence of strain-induced martensite transformation, leading to a decrease in the formability of 304L austenitic stainless steel.