The FSW (Friction Stir Welding) on magnesium alloy has already been widely used. Therefore, the research on its sound insulation characteristics appears particularly significant, based on the adaptive meshing technique, the FSW procedure was numerically simulated to provide constraint mode for the next acoustic calculation, which solved the problem of the material properties and achieved a combination of welding and acoustic to some extent. Subsequently, Designing and manufacturing a reverberation box measured TL (Transmission Loss) of the welded magnesium alloy plate, which could make up the shortage of a reverberation chamber in measuring the little specimen. Based on FE-SEA hybrid method, the method was employed to calculate the transmission loss which was then compared with the experimental one showed better consistency, prove feasible to predict the transmission loss in FSW on magnesium alloy. Comparisons between the welded magnesium alloy plate TL and the un-welded one could find that TL is reduced after welding. Changing the welding speed and the stir rotation speed respectively was used to observing TL in order to studying the influence of the welding parameters, which prove that the parameters should be required to set reasonable and not the bigger or smaller parameters is better.