Overview: Organic photodetectors (OPDs) have advantages such as wide material sources, tunable spectrum, solution processing, and low manufacturing cost. They have numerous potential applications in domains of aviation, military, business, medicine, et al. Traditional organic photodetectors owe a planar structure and mostly use indium tin oxide (ITO), silver, aluminum, and other materials as electrodes. The organic photosensitive layer is sandwiched between two asymmetric electrodes to form a "sandwich" structure. However, the rigidity and brittleness of planar substrates constrain their application in flexible and wearable devices. As an inherently flexible and simple-to-weave material, fibers have been widely used in electronic textiles and wearable devices in recent years. For example, there has been substantial research on fibrous solar cells, supercapacitors, light-emitting devices, and physical/chemical sensors. In terms of fiber-based photodetectors. In 2014, Jixun Chen et al used a Ni wire as the core to prepare a NiO-ZnO heterojunction, and a twine Pt wire as the outer electrode to realize ultraviolet detection. In 2018, Xiaojie Xu et al. modified CuZnS: TiO2 array on the Ti wire surface, and wrapped a carbon nanotube fiber (CNT) on the outer layer to realize the collection and transmission of photogenerated carriers. However, most fiber-based photodetectors are based on inorganic photosensitive materials, showing the disadvantages of complicated manufacturing procedures, poor flexibility, and high cost. In this study, a fiber-based organic photodetector (FOPD) was prepared using organic photosensitive material. The electron transport layer (ZnO), organic heterojunction photosensitive layer (PBDB-T:ITICTh), and hole transport layer (PEDOT:PSS) were prepared on the surface of zinc wire by dip-coating method. Silver wire or carbon nanotube fiber (CNT) was wrapped as the external electrode, and two kinds of flexible FOPDs were obtained. Both the two devices showed a typical response in the visible band with remarkable rectification characteristics, and exhibited a specific detection rate of 1011 Jones (300 nm~760 nm) at ?0.5 V bias. Due to the better interface contact between CNT external electrode and photosensitive layer, the CNT-FOPD showed a lower dark current density (9.5×10?8 A cm?2, ?0.5 V) and faster response speed (rise and fall time: 0.88 ms and 6.00 ms). This work is expected to provide new ideas for the development of flexible fibrous devices and wearable electronics.Fiber-based photodetectors are expected to be widely used in the field of wearable electronics due to their properties of flexibility, easy-to-weave, and omnidirectional light detection. Currently reported fiber-based photodetectors mostly use inorganic photosensitive materials, which have drawbacks such as limited mechanical flexibility and complex preparation processes. In this paper, we proposed the fiber-based organic photodetector (FOPD). The electron transport layer (ZnO), organic heterojunction photosensitive layer (PBDB-T:ITIC-Th), and hole transport layer (PEDOT: PSS) were prepared on zinc wire by a solution dip-coating method layer by layer. Finally, silver wire or carbon nanotube fiber (CNT) was wrapped as the external electrode, and two kinds of flexible FOPDs were obtained and showed typical rectification characteristics. They showed a specific detection rate of 10¹¹ Jones (300 nm~760 nm) at ?0.5 V bias. Due to the better interface contact between the CNT external electrode and photosensitive layer, the CNT-based device exhibited lower dark current density (9.5×10^?8 A cm^?2, ?0.5 V) and faster response speed (rise time of 0.88 ms and fall time of 6.00 ms). The work is expected to provide new ideas for the development of flexible fiber-based devices and wearable electronics.