In order to realize the high-value utilization of octopus waste， the octopus ink sac was used as the raw material. The study compared high-speed centrifugal method and enzyme method to extract octopus ink melanin， and explore its ultrastructure， ultraviolet-visible spectrum， physical and chemical properties. The results showed that the melanin extracted by high-speed centrifugation has two characteristic absorption peaks at the wavelength of 230 nm and 326 nm in the ultraviolet region. The average particle size is 123 nm， and the structure is intact. Analysis of physicochemical properties of octopus melanin indicates it was insoluble in most organic and inorganic reagents， would precipitate in acidic solution， was slightly soluble in alkaline buffer， and had good solubility in NaOH solution； under natural light conditions， the octopus melanin had good stability， but it was intolerant in the ultraviolet light. Under long time high temperature heating condition， the melanin was instable. Under different pH value conditions， the stability of octopus melanin increased with the increase of solution alkalinity. This study provides data support for the comprehensive utilization of melanin in octopus ink sacs.