In the work, aldehyde groups were quantitatively introduced into schizophyllan (SPG) side chains through periodate oxidation. The periodate-oxidized SPG (POSPG) forms an elastic gel with gelatin. The cogel formation is based on the Schiff-base reaction between the amino groups of gelatin chains and the aldehyde groups of POSPG chains. The POSPG/gelatin cogel has an elastomeric character with a very small value of loss tangent. The gelation kinetics and gel properties were discussed as a function of POSPG concentration, gelatin concentration, oxidation degree, temperature, and pH. This method can be used to design a large variety of cogels between SPG and proteins.