With regard to the reduction of transmission performance caused by uplink downhole noises and their echoes generating from the bottom drillstring in logging while drilling, based on the transmission characteristics of low-frequency acoustic waves in mismatched acoustic impedances and periodic pipe structure transmission channel, an acoustic isolation structure with a periodic groove structure is provided in this paper. According to the noise distribution and the center frequency of acoustic isolation stopband in drillstring channel, the frequency responses and sound reduction indexes for single acoustic isolator and combined acoustic isolator are compared. Then, the discussed acoustic isolation structures are introduced into the drillstring channel. By applying a finite-differential algorithm for the one-dimensional propagation of longitudinal waves along the drill string, the acoustic isolation performance of these two kinds of acoustic isolators in the drillstring channel are analyzed by the time and frequency domain simulation. The simulation results prove that combined acoustic isolator can achieve a wider acoustic isolation frequency bandwidth with a 20~40 dB reduction in noise, resulting in the improvement of signal-to-noise ratio and the increase of transmission rate, which provides the methodological foundation for the optimal design of acoustic telemetry system.