Species composition of algae and aquatic plants in Bung Si Phi swamp were investigated during February to July 1985. The samples were collected randomly 3 times in February, April and July respectively. Thirty-five species of algae and seven species of aquatic plants were observed. Closterium sp., Cosmarium sp., Mougeotia sp., Onychonema sp., Pediastrum sp., Tetraedron sp., Anabaena sp., Oscillatoria sp., and diatom were dominant species of algae population while Ceratophyllum demersum, Hydrilla verticillata and Najas minor were dominant species of aquatic plant and occupied major area of the swamp. The proximate analysis of Spirogyra sp. showed 12.81 percent of protein nitrogen content by dry weight. The protein contents of aquatic plants ranged from 10.79 to 13.99 percent by dry weight.