Photo induced ultrafast process in bacteriorhodopsin was observed with DFWM technique. The origin of the fast component(ps) and the slow component (ns) in photo excitation dynamics was explained on the basis of models of both the phase space filling and the conformational deformation. The former is due to the excitons made from free electron hole pairs and the latter is owing to the polaron induced from the non radiative decay. The saturation density and length of excitons, the life time of exciton and polaron, and the polaron state formation efficiency were extracted by a least square fitting procedure.