Transient saturation absorption spectroscopy in GaAs thin films was investigated using femtosecond pump and supercontinuum probe technique at excitation densities higher than 1× 1019 cm-3. The Coulomb enhancement factor of the electron-hole plasma results in a spectrum hole at the pump wavelength. Two distinct transmission peaks at two sides of the pump wavelength are observed, arising from the bleaching of transitions from the heavy- and light-hole bands to the conduction band. The dynamic process of the transient saturation absorption is fitted using a bi-exponential function. The fast decay process is dominated by the carrier-phonon scattering and the slow process may be attributed to the electron-hole recombination.