Abstract: To reduce the environmental hazard resulting from converter slag, the glass ceramics in SiO2-CaO-MgO-Fe2O3 system were prepared using the slag through melting process. The effect of the ratio w(MgO)/w(SiO2) on structure and flexural strength of the glass ceramics was investigated by DTA, SEM and XRD. The results showed that glass transition temperature and crystallization peak temperature of the ceramics changed little with the increasing value of the ratio, but its phase composition changed greatly, i.e., from augite to diopside with grain size gradually decreased and crystals uniformly distributed. Meanwhile the flexural strength of glass ceramics increased.