The effect of alkali concentrations and acid concentration on yield and gel strength of gelatin from bigeye tuna were investigated. Besides; the effect of acid concentration and alkali concentration on the extracting process were studied by FTIR infrared spectroscopy; scanning electron microscopy(SEC) and SDS-PAGE. The tests tried to provide the theoretical basis for the control of the production parameters of tuna skin gelatin. The result showed that the optimal gelatin extraction condition was 0.8% NaOH treatment and 2.0% acetic acid treatment. The results of FTIR analysis showed that the intermolecular hydrogen bonds of the collagen were destroyed; while the intramolecular hydrogen bond enhanced after the alkali treatment. The breakage of the original hydrogen bond changed the structure of the collagen and the triple helix structure stretched. This made the subunit easily released during the gelatin extraction process. The acid treatment with different concentration made the original structure of collagen destroyed and the triple helix structure stretched. The content of random coil increased. The results of scanning electron microscopy showed that the alkali treatment could cause slight degradation of collagen structure merely. After the acid treatment; gelatinized collagen degradated obviously; and gradually become irregular curl. The damage of collagen was more obvious at 0.8% alkali or 2.0% acid treatment. The SDS-PAGE result showed that when concentration of alkali treatment was low; the content of high molecular weight components was lower while the content of small molecular weight was higher than other groups. Increasing the concentration of alkali gradually; the high molecular weight components increased. When the concentration of alkali treatment was increased to 2.3%; the content of β-chain in gelatin increased and the content of α-chain decreased; which caused a decrease in gel strength. When acid was 0.5%-1.5%; especially at 1.5%; the content of high molecular weight components was high and gel strength was high. When the acid concentration was higher than 2.0%; the content of small weight molecule components in the gelatin was gradually increased. After the acid reached to 2.5%; the intensity of the small molecule weight components of gelatin was significantly enhanced and caused gel strength gradually reduced.