This study aims to prepare water-soluble β-1,3-glucan (WSG) by hydrolysis of curdlan with H2O2. The hydrolysis conditions were optimised as follows: reaction time of 40 min, H2O2 concentration of 2%, temperature of 85 °C and NaOH concentration of 2 mol/l. Under these reaction conditions, WSG yields of up to 83% could be achieved. High-performance liquid chromatographic analysis of WSG revealed a molecular weight of 5268 Da. Fourier-transform infrared spectroscopy confirmed the polysaccharide structure of the WS products. HPLC analysis of the complete hydrolysate of WSG indicated that WSG product consisted of glucose. Taken together, the results demonstrate that preparation of WSG by hydrolysis of curdlan with H2O2 is a promising approach with practical significance.