本文用定量的方法从理论上系统地探讨了酸碱体系普遍存在的同离子效应问题,首次提出了同离子效应指数ηη=1ga(Cs=0)-1ga(Cs≠0)及HCl(或NaA)对酸HA产生显著同离子效应(即η≥1)的判据Cs>max(10Ka,10(KaCa)~(1/2))同时,探讨了水对酸产生同离子效应的问题,提出了水对酸产生显著同离子效应的判据max(Ka,(KaCa)~(1/2))<10~(-8)并讨论了同离子效应指数、显著同离子效应判据的应用. In this paper, the problem of common ion effect in acid-base system is theoretically and systematically discussed by means of a quantitative method. For the first time, the common ion effect index ηη = 1ga (Cs = 0) -1ga (Cs ≠ 0) and HCl ) Has the same ion effect (ie, η≥1) criterion Cs> max (10Ka, 10 (KaCa) ~ (1/2)) for acid HA. Meanwhile, The criterion (max (Ka, (KaCa) ~ (1/2))) <10 ~ (-8) for the significant effect of water on acid was discussed and the application of the same ion effect index was discussed.