The starch based ionic and nonionic composite superabsorbent polymer (SAP) was synthesized fast under microwave irradiation by using cassava starch, partially neutralized acrylic acid and acrylamide. The effects of main synthetic technologies and swelling conditions on the swelling properties were investigated. The functional groups and morphology of the samples were characterized by FT-IR and SEM, respectively. It was found that SAP had a porous structure. The swelling processes of SAP in different temperature exhibited ?rst-order dynamics, and the swelling rate increased with the increase of temperature. The swelling ratio of the SAP was of pH and salt dependent. Furthermore, the swelling of SAP in organic solution was affected by the solubility parameter of solution, and the greater the difference of solubility parameter between organic solution and water was, the greater the swelling lost.