In this trial, effect of extrusion process parameters on the physical properties of extruded fish protein using a twin screw extruder was studied employing Response Surface Methodology. As input variables, twinextrusion cooking running parameters examined were barrel temperature in the last zone,screw speed and feed moisture, each at 5 levels. Meanwhile, as output v ariables, physical properties of the resultant extrudates included water content and bulk density. Results showed that moisture content of extrudates were affected intensely by feed moisture, and bulk density was effectively controlled by controlling the feed moisture, barrel temperature and screw rotation speed. Polynomial regression equations of process variables with two physical properties were obtained with R²=1.000, and R²=0.926, respectively. Both of two regression equations were highly credible. It is the first domestic study on the effects of thermoplastic extrusion cooking conditions on physical properties of extruda tes for the case of wet fish protein extrusion cooking. From the results discussed above, it is evident that for the extrusion of products with specific characteristics from wet fish protein, operating conditions can be defined fairly accurately. Variation of barrel temperature, screw speed and feed moisture enables extrudates with specific physical properties to be made for various applications. Moreover, response surface analysis can be seen to provide a quite effective means for the study and optimization of operating conditions in extrusion technology. By extrusion cooking, it is possible to produce products with attractive textures such as textured products with meat structure. Extrusion of proteinrich materials can be used to create various “fabricated\" foods, most commonly meat analogues or extenders. Experience has proven that it must be delivered in forms that fall within the organoleptic limits established by traditional human eating habits. So, by converting low value fish into protein food ingredients, the products should have a functional value in the food systems already familiar to a populace. Texturized fish protein products from low value fish protein by extrusion cooking can be used as meatlike products or meat extenders after rehydration with water or flavored liquids. The investigation of the relationships between chewy properties or eating quality and physical parameters for extrusion texturized fish protein are still unexplored. The work on these issues will be continued.