Astaxanthin (AST) has attracted great interests in the scientific world because of its anti-oxidative, anti-inflammatory properties. And biodegradable materials, like chitosan, have been employed as the AST carrier to protect it from degradation and promote its bioavailability. However, the lack of pH responsiveness of these materials usually could not protect AST from the strong acidic gastric juices. In this study, calcium alginate (CA) microspheres, a pH responsive and biodegradable material, were prepared by a modified double emulsion technology and used as the AST encapsulation agent. Experimental results showed that the microparticles formed had a good degree of roundness, dispersity, encapsulation efficiency, and pH responsiveness. Cellular studies demonstrated that AST encapsulated in CA could inhibit hepatoma cells (HepG2 cell line) but it has relatively small or no impact on control hepatocytes (THLE-2 cell line). Furthermore, investigation of the underlying mechanism indicated that recovery of disorder of glucose metabolism by inhibiting aerobic glycolysis and promoting tricarboxylic acid cycle played an important part in the cell proliferation inhibition of hepatoma cells. As suggested above, AST could be a very promising therapeutic agent of liver cancer in clinical trials.