Pure Al13 solutions at various concentrations were prepared by using the SO4/Ba separation method and characterized by using 27Al-NMR, IR, PCS, AFM and Ferron assay. The mechanism of humic acid removal by coagulation with Al13, lab-made PACl and industry PACl was compared. Special attention has been paid to the aspects of different coagulation species. The influence of pH and dose was discussed respectively from the change of zeta potential, residue turbidity, and UV254. The results show that the Al13 is the dominant and important species in the coagulation process deciding the charge-neutralization ability.