The invention discloses a disintegrant for relieving bio-membrane contamination in a membrane bioreactor; a preparation method comprises: preparing deoxyribonuclease I and D-tyrosine formate solutions having different mass concentrations respectively, mixing well the solutions, adjusting pH, and adding disintegrant activator Mn<2+> of certain mass concentration; application includes: adding the bio-membrane contamination disintegrant into membrane bioreactor backflushing water at a volume ratio of the disintegrant to the backflushing water being 1:(100-150). The bio-membrane contamination disintegrant is capable of significantly extending membrane contamination time of the membrane bioreactor in slow stage, the deoxyribonuclease I and D-tyrosine can disintegrate key components of the surface of a bio-membrane and may cooperate to arrive at synergy; the activator Mn<2+> can activate deoxyribonuclease I and D-tyrosine; the bio-membrane contamination disintegrant diffused to body solution is capable of reducing the proliferating rate of activated sludge and reducing the emission of residual sludge.