Transition　metal　dichalcogenides　(TMDs)　are　a　category　of　promising　two-dimensional　(2D)　materials　for　the　optoelectronic　devices,　and　their　unique　characteristics　include　tunable　band　gap,　nondangling　bonds　as　well　as　compatibility　to　large-scale　fabrication,　for　instance,　chemical　vapor　deposition　(CVD).　MoS2　is　one　of　the　first　TMDs　that　is　well　studied　in　the　photodetection　area　widely.　However,　the　low　photoresponse　restricts　its　applications　in　photo-detectors　unless　the　device　is　applied　with　ultrahigh　source-drain　voltage　(V-DS)　and　gate　voltage　(V-Gs).　In　this　work,　the　photoresponse　of　a　MoS2　photodetector　was　improved　by　a　chemical　in　situ　doping　method　using　gold　chloride　hydrate.　The　responsivity　and　specific　detectivity　were　increased　to　99.9　A/W　and　9.4　x　10(12)　Jones　under　low　V-DS　(0.1　V)　and　V-Gs　(0　V),　which　are　14.6　times　and　4.8　times　higher　than　those　of　a　pristine　photodetector,　respectively.　The　photoresponse　enhancement　results　from　chlorine　n-type　doping　in　CVD　MoS2　which　reduces　the　trapping　of　photoinduced　electrons　and　promotes　the　photogating　effect.　This　novel　doping　strategy　leads　to　great　applications　of　high-performance　MoS2　photodetectors　potentially　and　opens　a　new　avenue　to　enhance　photoresponse　for　other　2D　materials.