Describing the reciprocal relations of the two subsystems and giving the system of equations of the hybrid FE-SEA method. A hybrid model of the magnesium alloy dash board was built to validate whether the hybrid method was feasible to calculate the transmission loss (TL) of automobile dash board in middle frequency range by comparing with the experiment result. Analyzing the modal contribution of sound insulation trough to find the key participation modal and extracting the velocity vibration type to identify the sound transmission path of dash. TL of two typical sound packages which is ESP（Elastic-Sound Package）and FSP(Foam-Sound Package) in mid-frequency under reverberant sound was researched by changing thickness of the porous sound-absorbing material and the cover layer and the sound insulation performance of every program was evaluated according to noise reduction efficiency. ESP2 which the cover is 1mm had better sound insulation performance at the frequency lower than 260Hz while FSP2 had best TL at the frequency upper than 260Hz. Two programs which were applied to dash board for regional sound package at different frequency range, the sound troughs were obviously improved and the transmission loss of other bands had been increased by 2dB, which validated that the sound package was feasible, which could provided fast and accurate sound insulation measures for engineering applications.