One of the most important factor for the comfort of the passenger vehicles is the minimization of the compressible transmissibility during the running vehicles. Seat foam materials of 12 series (index 95 and the contents of isocyanate TDI was changed in percentages 75, 70, 65, 60, 50, 40) and D1 series (density 50 kg/㎥, index was changed 100, 95, 90) showed the significant differences in their transmissibility depended upon their chemical constitution such as index and contents of isocyanate TDI. The minimum transmissibility of seat foam materials of 12 series was found from the materials with the contents of 65% isocyanate TDI and the index 95 from the materials with the contents of 65% isocyanate TDI and index 95 at the frequency 4.79~5.31 Hz. Also the minimum transmissibility of seat foam materials of Dl series was found from the materials with the index90 and the density of 50 kg/㎥ at the frequency of 4.79~5.31 Hz.