Based on the principle of mirror image，the directivity in far field of sonochemical reactors is studied．The theoretical analysis and simulation shows that the higher transducer frequency，the narrower main acoustic beam and the smaller side lobe．The longer distance between adjacent transducer，the narrower main acoustic beam and the higher side-lobe peak．Besides，there is no relevance between the virtual source series and main acoustic beam．But the higher the virtual source series， the sharper directivity and the smaller side lobe.This suggests that the greater ratio between the sonochemical reactors′ longitudinal length and transverse length，the preciser description of the directivity in far field with the higher virtual source series．

transducer arrays； mirror principle； main acoustic beam； directivity； simulation