Abstract: Preparation and characterization of water soluble chitosan was examined for their antibacterial activity from P. stylifera. The yield of crude chitosan and water soluble chitosan was 54.3 % and 87.8%. The FT-IR spectrum of chitin, chitosan and water soluble chitosan also determined and characterization was done and compared with standards. Compare to other bacterial strains S.auerus (18.3mm) having more potential antibacterial activity in crude chitosan as well as water soluble chitosan. Both chitosans might have the antibacterial activity which would be used in novel drugs from the shrimp shell waste.