Abstract: Because the reflected wave from the downstream tube can not be totally eliminated in the standing-wave tube, which would affect the accurate measurement of sound transmission loss, the simulation model of measuring sound transmission loss in the standing-wave tube is presented by using LMS Virtual.lab software. The non-reflected boundary conditions are defined in the present model. Then, the sound insulation performance of honeycomb cavity covering is analyzed and discussed based on the present model. It is summarized that the mechanism of sound insulation performance includes impedance mismatch, waveform transformation and damping loss. Moreover, the effects of the cell thickness, cell angle and viscoelastic Young's modulus of the honeycomb structure on the sound insulation performance of honeycomb cavity covering are more obvious. The present model has been validated by comparing the numerical results of the analytical method, which can eliminate the reflected waves from the end surfaces of the upstream tube and the downstream tube.