Abstract: The self-strength of calcium ferrite binding phase in sinter and relationship between the fracture/compression strength and binding phase's composition were studied experimentally. Tested with the different mol ratios of CaO to Fe2O3 and the different contents of MgO, SiO2 and Al2O3, the fracture/compression strength of different binding phases was discussed. It is found that the highest fracture/compression strength is given when the ratio n(CaO):n(Fe2O3)=1:2, but the strength decreases when increasing MgO content. The appreciate content of SiO2 (<3wt%) will improve the strength of binding phase, while the strength of binding phase decreases with increasing Al2O3 content.