In　order　to　explore　the　sonication　condition　for　the　ideal　cavitation　effect　and　to　find　out　the　breakage　mechanism　of　flocs　exposed　to　ultrasound,　a　model　of　cavitational　bubble　and　two　sorts　of　simplified　models　of　diffusion-limited　aggregation　(DLA)　floc　breakage　were　established　and　simulated　based　on　Matlab.　The　practical　flocs　breakage　patterns　were　verified　through　experimental　analysis.　The　results　indicated　that　the　cavitation　effect　decreased　as　the　ultrasonic　frequency　increased.　The　increase　of　ultrasonic　density　led　to　the　increscent　amplitude　of　cavitation　bubble,　when　the　sonication　density　was　7　W/mL,　the　radius　of　cavitation　bubbles　can　be　enlarged　to　200　times　longer　and　the　cavitation　effect　was　fairly　good.　When　the　flocs　were　treated　at　low　energy　density　(0.03~3　W/mL)　and　low　frequency　(25~40　kHz)　ultrasonication,　surface　erosion　dominated　the　breakage　effect,　which　was　reflected　by　decreased　radius　and　increased　fractal　dimension　of　flocs.　When　the　energy　density　exceeds　3　W/mL　or　the　frequency　surpasses　40kHz,　the　large　scale　fragmentation　was　the　main　mechanism,　leading　to　the　smaller　flocs　size　and　looser　structures.　The　sonication　of　the　frequency　of　40　kHz　is　more　beneficial　to　flocs　breakage,　with　the　experimental　result　that　10minutes＇　ultrasonication　can　lead　to　a　dinimutioin　rate　of　9.8%　of　the　radius　and　a　fractal　dimension　of　1.394,　and　the　structure　of　the　flocs　were　more　compact.　©,　2015,　Chinese　Society　for　Environmental　Sciences.　All　right　reserved.