In order to examine the inhibition effect of other heavy metal ions on the removal of heavy metal ions by crab shell in aqueous solution, 10 heavy metal ions $(Cr^{3+},;Cd^{2+},;Ni^{2+},;Zn^{2+},;Hg^{2+},;Cu^{2+},;Mn^{2+],;Fe^{2+},;Fe^{3+},;Pb^{2+})$ were used as single heavy metal ions and mixed heavy metal ions, respectively. In single heavy metal ions, $Pb^{2+},;Cr^{3+},;Cu^{2+}$ were well removed by crab shell, however, $Cd^{2+},;Ni^{2+},;Zn^{2+},;Mn^{2+}$ were not. The heavy metal removal increased as the increase of covalent index (Xm$^2$r), and the relationship classified heavy metal ions as 2 heavy metal groups $(Fe^{3+},;Fe^{2+},;Cu^{2+},; Cr^{3+},;Mn^{2+},;Ni^{2+},;Zn^{2+};group;and;Pb^{2+},;Hg^{2+},;Cd^{2+};group)$. In mixed heavy metal ions, the removals of $Fe^{2+},;Fe^{3+},;Pb^{2+},;Cu^{2+}$ as 0.49 m㏖/g, regardless of the existence of other heavy metal ions, were similar to the result of single heavy metal ions experiment. The removals of $Mn^{2+},;Cd^{2+},;Ni^{2+}$ decreased as the existence of other heavy metal ions, however, the removal of $Zn^{2+},;Cr^{3+},;Hg^{2+}$ increased.