This experiment was carried out to investigate the influence of growth stage and frequency of cutting on the yield and chemical composition of Pragmites prosturatus from May to October. 1973. The results obtained arc as follows: 1. The highest air dry matter yield was obtained when Phragmites prosturatus harvested on July 28th and October 3rd rather than other harvesting dates. 2. The yield was decreased sharply after first cutting but three cuttings were possible at late in May, late in June and early October during the growing season. 3. The percentage air dry matter of Pragmitus prosturatus was lower at the early growing stage and increased as the growing stage progressed toward maturity, but the yearly average was about 32 percent. 4. It was found that the crude protein content decreased only in the summer but again in the autumn nearly as much as in the spring and the crude fiber content increased only in the summer but on the contrary it decreased in the autumn distinctly than the content in the spring.