The influence ofacoustic wave attenuation on the properties of fiber AOTF is studied and a simple methodto determine the acoustic wave attenuation by measuring the AO mode coupling effeciency isproposed. It is found that the acoustic wave′s attenuation will reduce the efficiency of AO mode coupling andbroaden the bandwidth of fiber AOTF. The increased bandwidth is in proportional to thesquare of the acoustic wave attenuation coeffecient.