In syndiotactic polystyrene (sPS), the stereoisomeric configurations around the main chain sites alternate regularly. This polymer is known to form a thermoreversible physical gel in moderately concentrated solutions. In this study, the gelation process of sPS solution was investigated through measurement of in situ Fourier transform infrared (FT IR) spectra. Moreover, the junction size S and the Young's modulus E of sPS gel was estimated as a function of solvent power, i.e., the degree of swelling at equilibrium, q(max). The time-resolved FT IR spectra suggested that sPS random coil chains in a relatively poor solvent such as toluene having the small value of q(max) turn quickly into the T(2)G(2) conformation, followed by gelation. On the other hand, the T(2)G(2) conformation appears very slowly in a relatively good solvent such as chloroform having the large q(max), value. The junction size S as well as Young's modulus E became larger with decreasing q(max).