In the production of fiber glass, the molten glass radiated from a centrifugal ring is elongated by high-temperature and high-speed airflow, and the centrifugal ring (5) is very likely to be overheated, which may cause the external wall (8) of the centrifugal ring (5) to bulge and extend into the area with strong thermal current (10). The invention can constantly inspect the radiant rays at the surface layer of the external wall (8) of the centrifugal ring (5) through at least one radiation pyrometer; the radiant rays are taken as real value in an airflow control system to obtain the optimal control on the temperature of the centrifugal ring (5) and the automatic production of the fiber is likely to be realized. At the same time, the harmful overheat and the sudden change of the temperature of the centrifugal ring (5) can be avoided and thus the practical service life can be prolonged. |