Abstract: Objective To observe the changes of new type of bile duct stent with Mg-Nd-zinc-Zr magnesium alloy material immersed in bile in vitro.Methods 3 magnesium alloy slices coated with magnesium fluoride and polylactic acid and 3 uncoated magnesium alloy slices were prepared，and they were immersed into bile perfusion system in vitro. The human bile was disinfected by 60Co irradiation. The bile was replaced every 12 hours，and the slices were taken out to measure their quatity，appearance，and weightless.Results At day 45 of immerse，the surface of uncoated slices had attached green bile，and the surface corrosion was obvious and etched surfaces were uneven，while the surface of coated magnesium alloy slices attached a small amount of bile，less surface corrosion and etched surface relatively uniform；At day 7 of immerse，the percentage of mass loss in coated and uncoated slices were （0.392±0.164） % and （0.357±0.215） % （P>0.05），while at day of 14，the percentage of mass loss in the two slices were （0.833±0.207） % and （1.915±0.587） %，respectively （P<0.05）；At day 91，the mass loss in coated magnesium alloy slices was significantly less than in the uncoated magnesium alloy slices （P<0.05）；the peak of mass loss in the two slices were at week 3 to 4，and the mass stabilized thereafter；the corrosion rates at day 7 between the two slices were （0.179±0.077） % and （0.357±0.215） % （P>0.05），while at day 14，they were （0.190±0.051） % and （0.469±0.146） %，respectively （P<0.05）；the peak of corrosion rate in the two slices was week 4，and the corrosion rate decreased after week 5.Conclusion The magnesium alloy bile duct stent coated with magnesium fluoride and polylactic acid can maintain its stability in the circumstance of bile，which might meet the requirements of clinical practice.

Key words: Billary tract diseases, Bile duct stent, Magnesium alloy, Bile, In vitro