2D　material-based　photodetectors　have　demonstrated　the　great　potential　in　future　optoelectric　applications　and　the　compatibility　with　the　traditional　semiconductor　technology.　However,　low　detectivity　and　difficulty　of　large-scale　fabrication　still　limit　their　application.　Here,　an　ultrasensitive　in-plane　lateral　graphene-MoS2　heterostructure　is　successfully　constructed　using　one-step　growth　by　chemical　vapor　deposition,　which　is　suitable　for　large-scale　fabrication.　The　Schottky　junction　is　formed　in　the　channel　with　the　edge　contact　of　graphene　and　MoS2.　It　displays　good　rectification　characteristics　with　an　on/off　ratio　up　to　10(6).　As　a　photodetector,　it　exhibits　excellent　detectivity　with　the　specific　detectivity　D*　up　to　1.4　x　10(14)　Jones　and　the　responsivity　of　1.1　x　10(5)　A　W-1,　which　benefit　from　strong　absorption,　the　efficient　separation　of　the　photoexcited　carriers,　and　quick　charge　transport　in　the　Schottky　junction　device.　Moreover,　heterostructure　photodetector　array　is　demonstrated　here　which　shows　the　large-scale　fabrication　capacity.　All　of　these　results　prove　the　potential　of　2D　material-based　junction　devices　for　optoelectronic　devices.