A novel method was developed to detect the glass transition of thin and ultrathin polystyrene (PS) films by correlating the relationships between the temperature-dependent viscoelasticity of the PS films and stick-slip behavior on their surfaces during dynamic wetting of glycerol or oligo-poly(ethylene glycol) droplets. The peak temperature (T-jm) obtained from the jumping angle-film temperature curve, in which the jumping angle Delta theta was employed to scale the stick slip behavior, was nearly identical to the corresponding T-g (or T-alpha) of the PS film. This was confirmed by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). The change of the measured T-jm with film thickness and substrate chemistry (SiO2-Si and H-Si) further confirmed that the developed method is very sensitive for detecting the dynamics of ultrathin polymer films.