Abstract: In order to investigate devitrification behavior of continuous casting mold flux in the process of annealing,glassy flux was annealed by single hot thermocouple technique,and then observed by scanning electron microscope and XRD. It is found out that the devitrified phenomenon occurred from the glassy flux during annealing and the main crystal phase is cuspidine. Temperature of devitrification increases with increasing annealing rate. When treating temperature is increased,degree of crystallization increases first then decreases. Increasing the steady temperature causes the shorter incubation time. With treating temperature of glassy flux film increase,the roughness on the surface of flux film increases,and the number of void increases.