Microstructure and quality of sinter of Sijiaying iron ore were studied systematically by means of optical microscope. Results show that the content of sinter of different ratio of Sijiaying iron ore are simple, the content of metal phase are magnetite and hematite, binding phases mainly are calcium ferrite and dicalcium silicate, and the contents of calcium ferrite are higher. The whole microstructure of sinter is uniform, which is interweaving corroded structure. The magnetites are major tiny allotriomorphic crystal. The shape of calcium ferrite is needle-like. The quality of sinter can meet the production request when the proportions of Sijiaying iron ore are from 50% to 100%.