The present disclosure provides a ray detection substrate, a manufacturing method thereof and a ray detection device, in the field of display technology. The ray detection substrate comprises: a basal substrate, wherein the basal substrate is provided with a photodiode, the photodiode includes two doped layers and an intrinsic layer located between the two doped layers, and an arrangement direction of the two doped layers is parallel with the basal substrate. The present disclosure solves the problems that the X-ray detection device is poor in performance and improves the performance of the X-ray detection device. The present disclosure is applied to a ray detection device.