The　interplay　between　excitons　and　physical　fields　emerges　as　a　forefront　research　topic　within　the　domain　of　condensed　matter　physics,　harboring　significant　impact　for　unraveling　material　properties.　Herein,　we　investigate　the　valley　exciton　behaviors　in　Janus　MoSeS/MoSe2　heterostructures　with　2H-　or　3R-stacking　configurations.　We　ascertain　that　the　intrinsic　polarized　electric　field　in　Janus　materials　can　markedly　enhance　the　valley　polarization.　Furthermore,　experimental　results　reveal　that　different　excitons　exhibit　inequivalent　spin-valley　dynamic　processes　under　intrinsic　electric　fields.　Among　them,　intervalley　trions　exhibit　a　superior　capability　to　preserve　their　spin　states　under　a　strong　intrinsic　electric　field　due　to　the　quantum-confined　Stark　effect,　thereby　achieving　the　highest　degree　of　valley　polarization.　This　work　provides　fundamental　insights　into　the　strong　correlation　effect　between　excitons　and　polarized　electric　fields,　signifying　an　advancement　in　control　over　the　valley　degree　of　freedom.