Abstract: Oxygen partial pressure has important effect on the sintering process of iron ores. Sintering experiments were carried out in different atmosphere conditions. It is found that the mineral composition of the sinter is mainly hematite and calcium ferrite, and acicular calcium ferrite appears in a stronger oxidation atmosphere. No obvious difference in mineral composition while the oxygen partial pressure is in the range of 7.10×10^-4 to 7.89×10^-5 Pa, but magnetite appears in local region. When the oxygen partial pressure decreases from 4.44×10^-5 Pa, magnetite obviously increases but hematite simultaneously decreases. To achieve an appropriate mineral composition and structure of high basicity sinter, the oxygen partial pressure should be controlled in the range of 2.12 ×10⁴ to 7.10×10^-4 Pa.