The phase transformation of Tangshan ironstone-tailings between 900°C ~1200°C in air was investigated by DTA-TG. XRD and SEM analyses indicated that the ironstone-tailings, sintered at 900° and 1000°C respectively, mainly were composed of α-quartz, anorthite [(Na0.45Ca0.55)(Al1.55Si2.45O8)], tremolite and a little of hematite. For the sample sintered at 1100°C, augite appeared and tremolite disappeared. Fayalite formed in the sample sintered at 1200°C. The two samples both exhibited contraction character in the range of experimental temperature.