NOVELTY - Anaerobic granular sludge is pretreated by washing with inorganic salt. Inorganic salt-containing culture medium, electron donor and sodium tetrachloropalladate are added to the pretreated sludge, nitrogen or hydrogen is injected into reaction system, and sealed. The reaction system is placed in shaker, and anaerobic granular sludge is collected, to obtain palladium metal-loaded anaerobic granular sludge. The obtained sludge is added to to-be-decomposed azo dyes in wastewater, electron donor is added, nitrogen is injected into reaction system, and anaerobic conditions are controlled.    USE - Usage method of bionano palladium-loaded anaerobic granular sludge in decomposition of azo dye e.g. acid orange-II, evans blue and congo red (all claimed).    ADVANTAGE - The bionano palladium-loaded anaerobic granular sludge enables decomposition of azo dye with high removal rate.    DETAILED DESCRIPTION - Anaerobic granular sludge obtained from sewage treatment plant is pretreated by washing with inorganic salt, and centrifuging. Inorganic salt-containing culture medium is added to the pretreated anaerobic granular sludge with concentration of 1-6 MLVSS g/l, predetermined amount of electron donor is added to the resultant mixture, sodium tetrachloropalladate is added, nitrogen is injected into reaction system when the electron donor is organic material, or hydrogen is injected into the reaction system when electron donor is hydrogen, and the reaction system is sealed. The reaction system is placed in a shaker, reacted at 15-40 degrees C for 0.5-24 hours, and anaerobic granular sludge is collected by centrifugation, to obtain palladium metal-loaded anaerobic granular sludge. The obtained palladium metal-loaded anaerobic granular sludge with concentration of 1-10 MLVSS g/l, is added to to-be-decomposed azo dyes in wastewater, electron donor is added, nitrogen is injected into the reaction system, anaerobic conditions are controlled, and temperature is controlled to 15-40 degrees C.