The invention discloses a preparation method of a light calcium-alginate-base sponge body functional material. The preparation method comprises the following steps: in room temperature, evenly mixing sodium alginate powder with soluble calcium salt, magnesium salt or aluminum salt, a reinforcing agent, peroxide and a catalyst to obtain a mixture; moistening with an alcohol-water solution to form paste; rolling by molding equipment to form a film material or a plate material; and then sequentially performing infiltration, complexation for pore formation, and expansion for pore formation. The preparation method has the characteristics of simple technology, low control difficulty, low equipment investment, energy-saving effect, low production cost and the like and is applicable to large-scaled industrial production; the prepared light calcium-alginate-base sponge body functional material is the same in structure and composition regardless of interior or exterior, good in quality, light in weight, high in mechanical strength, and excellent in imbibition performance and air permeability, and can be widely applicable to the fields of antibacterial materials, flame-resistant materials, adsorbing materials, acoustic materials, vibration-absorptive materials and the like; the market prospect is extensive.