The invention relates to ecological artificial bait for tuna longline and a preparation method therefor. The bait contains the following main constituent materials: a bait skeleton and bait film coating (outer coating) materials, wherein the bait skeleton is prepared from artificial or natural, degradable and harmless materials, and the density of the materials is higher than that of sea water, and the bait film coating (outer coating) materials contain adjuvants such as polyvinyl alcohol (PVA), polycaprolactone (PCL), poly(butylene succinate) (PBS), aliphatic polycarbonate (APC), polyurethane (PU), ethylene-vinyl acetate copolymer (EVA), styrene-ethylene / butadiene-styrene copolymer (SEBS), sodium alginate (SA), hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), protein, amino acid, starch, glycerine and cane sugar, as well as a fish luring agent, a coloring agent, an illuminating agent and the like. A film coating, which is proper in material density and has good dispersing and fish luring agent slow-releasing capacity, can be prepared through mixing the film coating materials at a proper ratio; and the ecological artificial bait is ideal in rigidity, toughness and weather resistance, excellent in mechanical properties, breakage resistance and tear resistance and easy to operate, transport and store. The novel ecological artificial bait can be prepared by a simple process and has a very good simulated effect, thereby being capable of replacing the traditional fresh bait.