Water quality ponds plays a pivotal role in the pond culture of Chinese Mitten Crab （Eriocheir sinensis）， influencing not only the yield and quality of the crabs but also the ecological health of the pond water and the compliance of discharged tail water with environmental standards. In this study， five representative adult Chinese mitten crab culture bases on Chongming Island were selected as sampling sites. The research systematically investigated and evaluated the changes in pond water quality throughout the crab culture period. The water quality parameters analyzed included dissolved reactive phosphorus （SRP）， total phosphorus （TP）， ammonia nitrogen （NH₄⁺-N）， nitrate nitrogen （NO₃^--N）， nitrite nitrogen （NO₂^--N）， total nitrogen （TN）， permanganate index （COD_Mn）， suspended particulate matter （SS）， Chlorophyll a （Chl.a）， among others. The results showed that the average concentrations of SRP and TP in the water of adult Chinese mitten crab culture ponds on Chongming Island ranged from 0.091 to 0.300， and from 0.235 to 0.449 mg/L， respectively， exhibiting fluctuations over the culture period. The average concentration of NH₄⁺-N was higher in April （3.82 mg/L）， but the NH₄⁺-N concentrations were lower in the middle and late stages of culture （< 2 mg/L）. The average concentration of TN was relatively high in April and May （7.04 and 6.19 mg/L， respectively）， the TN concentration in some ponds was also relatively high in September and October， but the TN concentrations were relatively low in the middle stage of culture （< 3 mg/L）. As the culture period progressed， the average concentration of COD_Mn initially decreased， reaching lower levels from April to September， before subsequently increasing again. The average concentration of SS fluctuated between 159 and 331 mg/L when the culture time prolonged. After June， the average concentration of Chl.a gradually increased and the maximum value was obtained in October. There was a significant correlation among TP， SRP， NH₄⁺-N， NO₂^--N and TN in the water of adult Chinese mitten crab culture ponds on Chongming Island， and COD_Mn was significantly positively correlated with TN and Chl.a. However， Chl.a was only significantly positively correlated with COD_Mn， and SS was only significantly positively correlated with NO₂^--N. For the adult Chinese mitten crab culture ponds on Chongming Island， the risk of cyanobacterial bloom was high. Compared to the Shanghai Aquaculture Tailwater Discharge Standards， the primary pollutant exceeded the limit was SS， while NH₄⁺-N and TN only surpassed the standard during the early stages of the culture period （from March to May）. To sum up， in the adult Chinese mitten crab pond on Chongming Island， the average concentrations of NH₄⁺-N significantly declined during the middle and late stages of the culture period. Meanwhile， TN levels decreased notably in the mid-stage. As for COD_Mn， its average concentration initially decreased and then increased again， with lower average concentrations observed from April to September. COD_Mn and TN exhibited a significant positive correlation， while SS and NO₂^--N also showed a strong positive relationship. According to the pollutant discharge standards for aquaculture tailwater， SS emerged as the primary pollutant in Chongming Eriocheir sinensis culture ponds. Consequently， sedimentation treatment of tailwater is essential to ensure compliance with discharge standards before its release into receiving water bodies.