Sodium alginate/feather keratin（SA/FK） microspheres were prepared by extrusion dripping method. The interactions of SA and FK were charactered by FTIR and viscosimetry. The effects of preparation conditions（m（FK）: m（SA）, w（CaCl2）, crosslinking time）and solution properties（pH, temperature, ionic strength,）on swelling ratio were also investigated. The result indicates that, electrostatic is the main interaction and hydrogen bond supplements it. Over time, swelling rate becomes slow, and it meets equilibrium swelling at last. SA/FK microspheres have compact network structures when m（FK）: m（SA）=0.60, w（CaCl2）= 7% and crosslinking time is 60 min. The equilibrium swelling ratios are 0.6, 0.6, and 0.9. The equilibrium swelling ratio rises from 0.6 to 0.9 when temperature rises from 30℃ to 45℃. The equilibrium swelling ratio rises from 0.9 to 1.1 when pH froms 1 to 7. As pH=13, it rises to 3.8. The equilibrium swelling ratio rises from 1.1 to 13.8 when ionic strength increases from 0 to 0.6mol/L. SA/FK microspheres possess the ionic strength / temperature / pH sensitivity, and it is expected to achieve new intelligent slow-release microspheres.