Abstract: The study was designed to investigate the effect of duration of frozen storage on chemical analysis, lipid damage and extractability of Myofibrillar proteins of Kutum (Rutilus frisi kutum. The fish were collected from Anzaly landings in north of Iran and were subjected to 12 months of frozen storage and analyzed at intervals of three month. Protein content ranges from 21.8±0.01 to 19.9±0.01. Protein decrease with increasing duration of frozen storage; fish samples that were for frozen thirty days; having highest protein content 21.8±0.01 while the least 19.9±0.01 was recorded for fish samples that were frozen for 12 months. Similar results obtained for the fat content where the highest fat content 3.21±0.01 was recorded for the fish samples that were for frozen 30 days and the least value was recorded for those stored for 12 months. The least moisture content was observed for fish samples the was stored for 12 months but, the highest Ash content was observed for fish samples the was stored for 12 month. Lipid damage were measured on the basis of Free Fatty Acids (FFA), Peroxide Value (PV), Thiobarbituric acid index (TBA-i). PV, TBARS and FFA concentration of frozen Caspian Sea white fish stored at -18°C; the temporal variation of these three variables were statistically significant (p<0.001). SDS-PAGE patterns showed that myosin heavy chain was much more susceptible to hydrolysis than actin.