The invention discloses a preparation method of agarose low in solidification temperature. The preparation method comprises following steps: agarose is mixed with deionized water at a ratio (w/v) of 20:1-30:1, and an obtained mixture is mixed and heated for gel dissolving; NaBH4 is added, and an obtained mixed material is reacted for 15min at a temperature of 80 DEG C; 0.5M of NaOH is added for activating agarose hydroxyl; modification agent dimethyl sulphate is added; and after reaction, pH value is adjusted with hydrochloric acid to 7, and ethanol is used for precipitation. The preparation method is simple in operation; solidification temperature of the agarose is low; and enlarge production is easy to realize. The preparation method is capable of providing foundation for further industrialization of preparation of the agarose low in solidification temperature, and possesses a promising application prospect.