A box ecosystem model is developed to simulate the seasonal variations of nutrient limitation in the Jiaozhou Bay.After model validation,the regional and interannual variations of nutrient limitation are analyzed.The results show that the nutrient limitation exhibits obvious seasonal variation.In spring, the phytoplankton grows fast and exhausts the available nutrients.The nutrient limitation becomes the strongest in late spring and turns to be the weakest in summer when the river in flood season supply sufficient nutrients into the Jiaozhou Bay.Meanwhile,the regional variations of nutrient limitation are obvious. The limitation nutrient is SIL in aquaculture area,and is SIL and DIP alternatively in both the river mouth area and the mouth of the Bay.The nutrient limitation is the strongest in the mouth area of the Bay,while the weakest in the river mouth area.In 1960 s,the main limiting nutrient is DIN.Under the influence of human activity and climate change,the limiting nutrient has altered from DIN to SIL until now. The DIP limitation occurs in the certain region and period.The nutrient limitation is continually enhanced as time goes on.As a result,the phytoplankton biomass at the beginning of this country decreases by 21% comparing with that in 1960 s.