Abstract: With widely using of the nanotechnology，more and more nano-particles have entered into wastewater and sludge， which affect the anaerobic digestion process． Effects of nano-particles on anaerobic digestion process ( adsorption and reduction of harmful heavy metals，enhancing methane production as electron donor，degrading refractory organics and reducing hydrogen sulfide) and the impacts of nano-particles on anaerobic microorganisms ( releasing heavy metals toxicity，coating microbial cells by adsorption，damaging the cell membrane and DNA) were reviewed． In this paper，the strategies to reduce the harm of anaerobic microbes by nano-particles were discussed，in order to improve the anaerobic digestion of wastewater /sludge by taking advantage of nano-particles characteristics．