The utility model discloses a prevent protection casing of flange steel ring erosion comprises the shell body, the shell body includes that the semicircular snap ring of two components of a whole that can function independentlys constitutes every be equipped with the card ear of a pair of outside extension in the semi -circumference of snap ring, every card ear through the connecting hole on it with flange bolt connects, and the outwardly directed tip of every card ear is equipped with this casing of handle and prevents effectively that the flange steel ring receives the fast -speed life -span that contains the erosion of the sand flow body, extension flange steel ring of spun in the pit when the well head takes place the blowout, ensure the safety in production.