NOVELTY - Biological anti-freezing agent is prepared by preparing dried powder of anti-freezing active substance of seaweed by adding polar organic solvent to seaweed, performing extraction, filtration, centrifugation, freezing and drying process, adding non-polar organic solvent to the obtained filter residues, performing extraction, filtration, centrifugation, freezing and drying process, dissolving the water-soluble active ingredient in polar organic solvent and dissolving the fat soluble active ingredient in non polar organic solvent, and mixing the obtained solutions and adding e.g. urea.    USE - As biological anti-freezing agent.    ADVANTAGE - The biological anti-freezing agent is environmentally-friendly.    DETAILED DESCRIPTION - Biological anti-freezing agent is prepared by preparing dried powder of anti-freezing active substance of seaweed by adding polar organic solvent to seaweed, performing extraction, filtration, centrifugation, distillation, freezing and drying to obtain water-soluble active ingredient, adding non-polar organic solvent to the obtained filter residues, performing extraction, filtration, centrifugation, distillation, freezing and drying to obtain the fat-soluble active component, dissolving the water-soluble active ingredient in polar organic solvent and dissolving the fat soluble active ingredient in non polar organic solvent, mixing the obtained solutions and adding urea and surfactant. An INDEPENDENT CLAIM is included for method for preparing the biological anti-freezing agent which involves preparing anti-freezing active substance of seaweed by adding polar organic solvent to seaweed, performing extraction, filtration, centrifugation, distillation, freezing and drying to obtain water-soluble active ingredient, adding non-polar organic solvent to the obtained filter residues, performing extraction, filtration, centrifugation, distillation, freezing and drying to obtain the fat-soluble active component, dissolving the water-soluble active ingredient in polar organic solvent and dissolving the fat soluble active ingredient in non polar organic solvent, mixing the obtained solutions and adding 5-20 wt.% urea and 1-10 wt.% surfactant.