In this paper, the principle of weighted directional coupler and its application in apodization of integrated acousto optic tunable filter (IAOTF) have been analyzed and discussed. According to the theoretical analysis, the acoustic waveguide has been designed and the TE/TM mode conversion characteristics of AOTF have been analyzed. Based on the results, practical filter has been fabricated on the substrate of X cut, Y propagate  LiNbO 3. Experimental measurement shows that sidelobes are suppressed to -14 dB and -3 dB bandwidth is 2.0 nm.