Abstract: In this research report,by determining the concentration of the K＋、Na＋、Ca2＋、Mg2＋、Cl-、PO3－4 and etc in Common carp blood,we just preliminarily study into how low pH level affects the balance of electrolyte in common carp blood under water circumstances.The results show that when common carps are in the condition of low pH circumstances,the balance of electrolyte in serum is affected.In the experiments,the conrt of K＋ was evidently higher than the normal level;the content of Na＋ was evidently lower than the normal level.But there was no evident law of the changes of Ca2＋，Mg2＋,Cl－，PO3－4 etc,that were caused by low pH level.

Key words: pH, common crap, blood, electrolyte