Xanthan gum-g-acrylic acid / montmorillonite (XG-g-PAA/OMMT) organic-inorganic compound composite super absorbent mateial was prepared by solution polymerisation. When the amount of montmorillonite is the quality for the 6% of acrylic acid, the water absorbency was up to 882 g.g-1, 0.9% NaCl solution absorbency reached 106.5 g.g-1. And Fourier Transform Infrared Spectroscopy (FT-IR), x-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC) and Thermogravimetric Analyzer (TGA) were used to research characterization of the compound. The results have been shown that the acrylic acid molecule linked to the molecular chain of xanthan gum through graft co-polymerisation, adding montmorillonite changed the crystal structure of XG-g-PAA. The composite super absorbent material formed a bigger space network structure, water absorption and salt resistance and thermal stability were improved. The water absorption kinetics mechanism has been discussed through studying the swelling process of composite super absorbent mateial, that mainly related to non-Fickon diffused model.