The invention provides modified pulverized-fuel-ash ceramic as well as a preparation method thereof. The modified pulverized-fuel-ash ceramic is prepared from a pulverized fuel ash matrix and a rare earth oxide, wherein the rare earth oxide is loaded on the surface and in the channel of the pulverized fuel ash matrix; the pulverized fuel ash matrix has a porous structure; the porosity of the pulverized fuel ash matrix is 25 to 64 percent. The modified pulverized fuel ash provided by the invention has the porous structure; through the specific surface area of the provided pulverized fuel ash, the improvement of the removal rate to chromium ions is facilitated; rare earth positive ions are fixedly loaded on the surface and in the channel of the pulverized-fuel-ash ceramic; the removal of Cr<6+> in sewage with the Cr<6+> is convenient. The invention also provides application of the modified pulverized-fuel-ash ceramic to the treatment of an aqueous solution containing the chromium ions. The modified pulverized-fuel-ash ceramic provided by the invention has the removal rate, which can reach 93.82 percent or above, of the Cr<6+> in the sewage containing the chromium ions, and unmodifiedpulverized-fuel-ash ceramic has the removal rate, which can only reach 4.27 percent, of the Cr<6+>.