The acoustic isolator is positioned between the bit and the transmitting transducer, it can attenuate a variety of front end of the drill noise signal to avoid the acoustic noise signal propagation along the drill collar, affecting the acoustic signal transmission and used to weaken the influence of downlink acoustic signal with the uplink channel produced by the transducer. This paper improved the characteristic analysis of tapered acoustic transmission model, designed of the size and structure of the acoustic isolator which has the transmission frequency channel of in 700~800Hz and 1200~1300Hz interval.