The utility model relates to the technical field of lifting in oil well production, in particular to a long-acting degassing sand-prevention device suitable for a 5.5-inch casing pipe production well. An upper connector, an outer cylinder and a lower connector of the device are sequentially connected from top to bottom; a slit sieve pipe is designed in the middle of the outer cylinder; the upper end of a central pipe is connected to the inner wall of the upper connector; a gas exhaust hole is formed in the upper end of the outer cylinder; a gas entraining cylinder is arranged at the lower end of the gas exhaust hole; the lower end of the gas entraining cylinder is connected with a gas collection cap; the outer side of the central pipe is sleeved with both the gas entraining cylinder and the gas collection cap; the lower part of the central pipe is sleeved with a plurality of groups of umbrella spiral sheets; gas channeling holes are formed in the umbrella spiral sheets; and the bottom end of the central pipe is connected with the inner wall of a sand separation cylinder through a connection edge. The long-acting degassing sand-prevention device realizes efficient gas prevention and sand prevention, so that an oil well can perform production efficiently. The device overcomes the disadvantages that a conventional gas and oil prevention device is poor in liquid suction capacity and gas prevention effect.