Photo excitation dynamics in a three-step photo ionization of atomic uranium has been investigated using time-resolved two-color three-photon and delayed three-color three-photon photo ionization signals. Investigations are carried out in an atomic beam of uranium coupled to a high-resolution time-of-flight mass spectrometer using three tunable pulsed dye lasers. Dependence of both the signals on the second-step laser photon fluence is studied. Excited-level-to-excited-level photo excitation cross section and photo ionization cross section from the second excited level are simultaneously determined by analyzing the two-color three-photon and three-color three-photon photo ionization signals using population rate equation model. Using this methodology, photo excitation and photo ionization cross sections at seven values of the second-step laser wavelength have been measured. From the measured values of the photo excitation cross sections, we have obtained excited-level-to-excited-level transition probabilities and compared these with the values reported in the literature.