We investigate the effect of delay time, pulse width and pump wavelength on photoelectron spectra and wave packet forming process of the three-level K2 molecules via time-dependent wave packet approach. There is no Autler-Townes splitting for weaker pump intensity or shorter pulse width. Delay time and pump wavelength can affect peak structure, position, and relative height. The vibration period of wave packet does not vary with pump wavelength, while the oscillating amplitude decreases with increasing pulse width. Results may provide important basis for realizing the optical control of molecules experimentally.