Organic　phototransistors　are　leading　the　development　of　next-generation　wearable,　monitoring,　imaging,　and　sensing　technologies　due　to　their　light　weight,　low　cost,　high　yield,　compatibility　with　flexible　substrates,　and　customizable　methods　for　synthesizing　optoelectronic　properties.　However,　the　long　channel　length　of　conventional　planar　structures,　usually　in　the　micron　range,　greatly　reduces　the　carrier　transport　efficiency　and　leads　to　an　increased　probability　of　defect　trapping　and　complex　recombination　of　photogenerated　carriers.　Here,　an　organic　phototransistor　with　a　vertical　channel　structure　has　been　demonstrated,　in　which　the　active　layer　is　blended　with　Mxene.　Due　to　the　short　channel　length　of　vertical　structure,　the　recombination　possibility　of　photogenerated　excitons　is　reduced,　and　the　high　ultraviolet　sensitivity　of　Mxene　increases　the　bandwidth　of　detection.　The　device　exhibits　excellent　photodetection　performance　with　the　photosensitivity　of　4.28　x　106,　photoresponsivity　of　2.39　x　104　A/W,　detectivity　of　1.04　x　1017　Jones　under　irradiation　with　weak　light　of　8　mu　W　cm-2　at　365　nm.　This　work　paves　the　way　for　the　study　of　transistors　scale　and　high-performance　organic　photodetection　in　the　future.