The potential biomedical application of carbon nanotube (CNT) becomes a driving force to incorporate polymer-assisted dispersed CNT into the alginate (AL) microsphere as a drug carrier. The results of XRD and SEM showed that the addition of CNT had no evident effect on the structures and morphologies of microspheres. As expected, the incorporation of CNT enhanced the storage modulus of the AL sol, and hence improved the mechanical stability of the AL/CNT microspheres. Although the swelling degree had no obvious change after the same interval under various pH conditions, the preserving time of the AL/CNT microspheres obviously increased under the pH conditions of 6.8, 7.0 and 7.4. Furthermore, the encapsulation efficiency of drug in the AL/CNT microspheres was enhanced while the drug leakage was decreased. The results of drug release with theophylline as a drug model showed that the AL/CNT microspheres inherited the pH sensitivity of the AL microspheres while the character of sustaining release was more predominant. In virtue of the cytotoxicity of the CNT-filled AL microspheres equivalent to the neat AL microspheres proved by the tests of cell viability assay, the AL/CNT microspheres, with higher stability, less drug leakage and predominant sustaining release profile, showed the potential application as a drug delivery system to intestine and colon.