The phase transition of two kinds of solvent-induced crystalline syndiotactic polystyrene (sPS) , γ-sPS and δe-sPS, has been studied via WAXD and DSC.γ-sPS transform to α-sPS at 195-225℃ before melt during heating, whereas δe-sPS transform to first γ-sPS and then α-sPS at 100-200℃ and 200-215℃, respectively.The transition of δe-γ and γ-α occurs far below melting point of sPS indicates they are all solid-solid transition.