Study on agarose processing method is important for realizing domestic agarose production. Four methods, including polyethylene glycol, ammonia sulfate, EDTA-Na2 and urea methods were used to extract agarose. The four methods showed significant difference in agarose productivity and quality, among which the EDTA-Na2 method obtained the highest agarose productivity of 62.3%, the polyethylene glycol method produced agarose containing the least sulfate (1.39%) and ash (0.42%), the urea method produced agarose with the best electrophoresis characteristics of crystal violet which showed an electrophoresis length of 8.6 cm, while the EDTA-Na2 method produced agarose with the best electrophoresis characteristics of polyethylene glycol which displayed an electrophoresis length of 3.9 cm. With the polyethylene glycol method, the longer the extraction time, the greater the purity and quality of the agarose. Triple polyethylene glycol extraction obtained better agarose than those of other methods. These results would provide parameters for optimizing agarose production methods.