The introduction of biodegradable implant materials has significantly improved the postoperative subjective feelings of patients within the past few decades, among which magnesium alloy is widely considered a favorable choice as its appropriate biodegradability and evident antibacterial activity. Here, we reveal a semisolid rheo-formed Mg–Zn–Sr alloy ureteral implant that displayed suitable degradability and biocompatibility in a pig model. Refined non-dendritic microstructure was observed in the rheo-formed alloy, which led to ca. 47% increase in ultimate tensile strength (from 195.0 MPa to 288.1 MPa) and more homogeneous degradation process compared with the untreated alloy. No post-interventional inflammation or pathological changes of the test animals were observed during the implantation period, and the corrosion rate (0.22 ± 0.04 mm·y⁻¹) perfectly fitted the clinical ureteral stent indwelling time. The urine bacteria numbers decreased from 88 ± 13 CFU·mL⁻¹ at 7 weeks post operation to 59 ± 8 CFU·mL⁻¹ at 14 weeks post operation, which confirmed the evident antibacterial activity of the alloy. Our study demonstrates that the Mg–Zn–Sr alloy is clinically safe for urinary system, enabling its efficacious use as ureteral implant materials.