Flexible cardan shaft assembly in screw drill

The utility model provides a flexible cardan shaft assembly in a screw drill. The flexible cardan shaft assembly comprises a flexible cardan shaft positioned in a center hole of a hollow drive shaft, wherein the upper end and the lower end of the flexible cardan shaft are respectively connected to the lower end of a roller and a drill bit joint; connecting holes are formed both in the lower end of the roller and the drill bit joint; the upper end of the flexible cardan shaft is inserted into the connecting hole of the lower end of the roller, and are in matched connection with the connecting hole; the upper end of the flexible cardan shaft and the lower end of the roller are further connected by penetrating a cylinder resilient pin; the lower end of the flexible cardan shaft is inserted into the connecting hole of the drill bit joint and are matched connection with the connecting hole by splines; and the lower end of the flexible cardan shaft and the drill bit joint are connected by penetrating the cylinder r