A novel biodegradable hydrogel composed of starch, 2-acrylamido-2-methylpropane sulfonic acid (AMPS) and acryl amide(AM) have been prepared by free radical polymerization method using N,NImethylenebisacrylamide( MBA) as cross-linking agent. The structure, morphology, and thermal nature of hydrogel are investigated by FT-IR (Fourier Transform Infrared Spectroscopy) , SEM(Scanning Electron Microscopy), and TGA(Thermo gravimetric Analysis) respectively. The water sorption behaviour of the hydrogel is investigated under different conditions of the swelling medium. The Swelling study shows that the water uptake property of the hydrogel is dependent on composition of polymer, pH and ionic concentration of the medium.