The adsorption mechanism of Na+, Cl- and other impurities on the surface of basic nickel carbonate was clarified by electric double layer model. Based on the mechanism, a new purification method was studied. The method can be described as washing-drying-rewashing-drying. The experimental results indicate that the process is very efficient to remove impurities adsorbed by the precipitate when using NiCl2 and Na2CO3 as the raw materials. The finished product's contents of sodium and chlorine are both less than 0.01wt%.