Autler-Townes (AT) splitting in photoelectron spectra of four-level ladder K2 molecule driven by three laser pulses is investigated with time-dependent wave packet approach. Dependence of AT splitting on second laser pulse is studied. Photoelectron spectra show triple splitting with symmetric profiles in resonance, while triple splitting with asymmetric profiles is transformed into double splitting gradually in nonresnance. Three peaks shift to lower energy differently as laser wavelength increases. Splitting between two sideband peaks does not...