We made an experiment of keeping extension of raw and semi-dried flounder (Pleuronectes herzensteini). Effect of with(WG) or without gill (OG), drying degree (20% drying：20D, 40% drying：40D) and storage temperature (5 and $10^{circ}C$) and 0.1% chitosan-ascorbate (CA) treatment of vacuum packaging flounder on growth of contaminated microorganism during storage for 10 days were investigated. Total aerobacter (TA) in the OG-treated raw flounder was $0.3{sim}0.5$ log cycle lower than that of WG-treated flounder and also, number of coliform (CF) and E. coli (CO) in OG were lower compared with WG. Number of TA,. Especially, the TA was $0.42{sim}1.20$ log cycle lower compared with raw flounder. The TA of the raw flounder stored at $5^{circ}C$ compared to $10^{circ}C$ was $0.6{sim}1.3$ log cycle lower. The growth of total aerobacter, coliform (and E. coli separated from raw flounder in tryptic soy broth were completely inhibited by 0.1% CA. But the growth of TA in the raw and 20% dried flounder was 1.5 log cycle inhibited by 0.1% CA, and the growth of CF and CO were also slightly inhibited. We did value raw sample that treated CA 0D and 20D, and did vaccum packaging at the $10^{circ}C$ for 10 days, Sensory quality such as appearance, freshness, and texture and overall acceptability after cooking of the 0.1% CA-treated raw and 20% dried flounder were evaluated from good to very good, while CA non-treated products were evaluated to moderate.