Backflow-preventing type horizontal well gravel filling device

The utility model provides a backflow-preventing type horizontal well gravel filling device, which comprises an upper connector, an upper closing seat, an upper closing press cover, an upper closing assembly, an upper switch spring, a lower closing seat, a lower closing press cover, a lower closing assembly, a lower switch spring, an adapter connector, a filling short joint, a filling opening, a switch slide sleeve, a reset spring, a spring seat, a guide head, a sealing inserting pipe and an inner filling opening, wherein one end of the upper connector is connected with one end of the upper closing assembly, the other end of the upper closing assembly is connected with one end of the lower closing assembly, the other end of the lower closing assembly is connected with one end of the adapter connector, the other end of the adapter connector is connected with one end of the filling short joint, the other end of the filling short joint is provided with the guide head, and the filling short joint is provided with the filling opening. The backflow-preventing type horizontal well gravel filling device has the advantages and beneficial effects that in the large displacement well and horizontal well gravel filling sand-control construction process, a dense gravel layer is filled in an annular gap between a screen pipe and a well wall, and the flowback of the gravel is prevented.