With the experiment of D263 NO3^- type poor uranium resin adsorbing leaching liquid of in - situ acid leaching of uranium, the procedure and ruh of NO3^- ion entering into adsorption tail liquid are analyzed, and the initial concept of NO3^- accumulation balanced point in adsorption tail liquid is founded. Furthermore, some features of the accumulation balanced point and its potential application are studied, and the concept is extended to the behavior of exchangeability ion in adsorption course on resin.