The invention provides a method of synchronously degrading excess sludge and treating hexavalent chromium wastewater, and relates to a method of recycling the excess sludge and treating the chromium-containing wastewater. The invention aims to solve the problem that the current treatment cost for treating excess pollutants is high by utilizing microbial fuel cells. The method comprises the steps of 1, setting up a double-cell-structure reactor; 2, adding the excess sludge and nutrient solutions into an anode chamber of the reactor, adding potassium ferricyanidecatholyte into a cathode chamber, and performing cultivation, wherein when the voltage output is greater than 0.6 V, starting is successful; 3, adding the excess sludge and the nutrient solutions to be treated into the anode chamber, adding the hexavalent chromium wastewater to be treated into the cathode chamber, and performing treatment, wherein a treatment period of the excess sludge is 40 to 50 days, the degradation rate of the excess sludge can reach 38 percent to 62 percent, a reduction period of the hexavalent chromium wastewater is 2 to 10 days, the degradation rate of hexavalent chromium can reach 66.4 percent to 93.2 percent, and the purpose of synchronously degrading the excess sludge and treating the hexavalent chromium wastewater is realized.