This invention relates to the vitrification of radioactive waste products. According to this invention, a glass composition that is suitable for mixed waste products, which include flammable waste products, such as gloves, working clothes, plastic waste, and rubber, and low-level radioactive waste products, and a method of vitrifying the mixed waste products using the same are provided to significantly reduce the volume of radioactive waste products and to vitrify the mixed waste products using the glass composition, which is suitable for vitrifying the mixed waste products, thereby maximally delaying or completely preventing the leakage of radioactive materials from a glass solidified body.