Abstract: Two fishery death accidents, happened in freshwater fish farms in Minhou County and Fuqing City,Fujian Province were caused by poultry manure contamination. Through this investigation we found that the ammonia, ammonia nitrogen and total coli group were beyond the standard level in the contaminated water. The oxygen consumption substances increased by poultry manure contamination in Minhou County fishery farm. The consumption of oxygen in water caused the fish died for hypoxia. The dissolved oxygen in dead zone is 0.55 mg/L to 0.92 mg/L. Caused by poultry manure contamination in Fuqing City fishery farm, the amount of phytoplankton rapidly increased from 9.58×10⁷ cell/L to 1.05×10⁸ cell/L after consuming ammonia nitrogen nutrients. Photosynthesis also produced larger amounts of oxygen in daylight which resulted in super saturation dissolved oxygen(180%~183%). At the same time, releasing of carbon dioxide also led to pH increase(9.59~9.79). Furthermore, a large amount of NH₄⁺ in water was transformed into NH₃, consequently fish died for the increase of ammonia content. After investigation of these two typical poultry manure contamination in aquaculture water cases, we analyzed the variation of index factors and concluded that the poultry manure contamination could lead to increase of ammonia, ammonia nitrogen and total coli group. The factors causing fish death were lack of oxygen and ammonia poisoning. Recommended strategies for pollution prevention suggested in the paper as well.