Abstract: Regarded yield and concentration of soluble protein as eveluation factors, the optimum preparation process of isolate protein from Sthenoteuthis oualaniensis by p H-regulation method was researched. The effects of p H value, solid-liquid ratio, dissolution time and dissolving temperature on the extraction rate of soluble protein were analyzed, and the extraction conditions were optimized.The soluble protein under different soluble and precipitated p H value were measured by Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis ( SDS-PAGE) . The results of optimum preparation conditions were as follows, p H12.0, solid-liquid ratio 1∶ 9 ( g/m L) , dissolving temperature 4 ℃ and dissolution time 10 min.The result showed that dissolution rate of isolated protein was the highest and reached 80% under this condition.The yield of protein recovered was the highest when p H = 5.5 with the optimum condition of acid or alkaline dissolution p H value and the precipitation rate of isolated protein precipitated by acid precipitation reached 60%, which was higher than that of alkaline precipitation.The effects of p H values on the components of protein isolates from Sthenoteuthis oualaniensis were different. Myosin heavy chain ( MHC) and paramyosin ( PM) were affected by p H values and degradated quickly, actin ( A) was less affected by acid and alkaline conditions, tropomyosin ( TM) was affected by acidic conditions and the degradation effect was great.The preparation process can be used to large-scale produce isolate protein from Sthenoteuthis oualaniensis and it provides a new isolated protein preparation method.