The invention provides a method for continuously detecting glucose concentration in a sample, including: (a) providing a biosensor comprising a transducer and a polysaccharide covered on the surface of the transducer; (b) providing a carbohydrate binding protein solution, wherein the carbohydrate binding protein has at least one receptor, and the receptor is capable of binding to the polysaccharide and glucose; (c) mixing a sample and the carbohydrate binding protein solution to form a mixture; (d) contacting the mixture with the biosensor; (e) detecting the amount of carbohydrate binding proteins bound to the polysaccharide by the biosensor, wherein glucose concentration of the sample is inversely proportional to the amount of carbohydrate binding proteins bound to the polysaccharide; and (f) refreshing the surface of the biosensor with a high concentration glucose solution.