Abstract: The variations in the concentration and distribution of nutrients in the Yangtze River Estuary were investigated based on the data obtained during field observations in November 2003(dry season) and August 2004(wet season).The results showed that the concentrations of nitrate were much higher than those of nitrite and ammonia,which accounted for 92.8%～97.7% and 84.3%～98.4% of dissolved inorganic nitrogen in wet and dry seasons,separately.Nitrate and ammonia showed higher concentrations in wet season than in dry season.Nitrite,however,gave the similar concentration levels in both seasons.The average concentrations of phosphate were 0.014 and 0.016(mg/L) in wet and dry seasons separately,which attained the first standard level of seawater,according to the national standard of seawater quality.For both seasons,the concentrations of nitrate and phosphate decreased from inside the estuary to outside the estuary,which displayed the opposite spatial variations with ammonia.Based on the results of nutrient ratios,it was suggested that the nutrients supply was sufficient in dry season and thus phosphate was not a limiting factor for phytoplankton growth in the Yangtze River Estuary.However,the primary production in the Yangtze River Estuary might be limited by phosphate in wet season.