The supper absorbent resin of starch grafting acrylic acid was prepared by inverse emulsion polymerization with heating gelatinized cassava starch or mechanical activated cassava starch and acrylic acid (AA) as the raw material. The effects of mass ratio of AA to starch, concentration of initiator (APS) and crosslinking agent (MBIS) on absorbency of the resins were investigated. The functional groups of the resins were characterized by FT-IR. The results showed that the acrylate monomer was successfully grafted onto starch, and the mass ratio of AA to starch, concentration of initiator and crosslinking agent were the major factors which affected the absorbency of resin. Compared with the heat gelatinized starch graft super absorbent, mechanical activated starch grafted acrylate super absorbent had a higher maximum absorption rate of deionized water 194.51 g/g, which improved 43.14%, and a higher maximum absorption rate of normal saline 16.88 g/g, which improved 27.1% Compared with the heat gelatinized pretreatment technology，the mechanical activation pretreatment technology for preparing starch-based super absorbent resin via inverse emulsion would reduce the consumption of resources and the cost.