This paper presents a numerical study of the gas-solid flow in an ironmaking blast furnace by combining discrete particle simulation (DPS) with computational fluid dynamics (CFD). The conditions considered include different gas and solid flow rates, asymmetric conditions such as non-uniform gas and solid flow rates in blast furnace raceways, and existence of scabs on the side walls. The obtained results show that main gas-solid flow features under different conditions can be captured by this approach. The computed results are consistent with the experimental observations. Microscopic structures including the force structure are examined to analyze the effect of gas flow on the solid flow at a particle scale. Further, macroscopic properties such as solid pressure and porosity are obtained from the corresponding microscopic properties by an averaging method. It is shown that the solid pressure-porosity relationship in a blast furnace is complicated, varying with different flow zones. None of the literature correlations considered can fully describe such a feature. Based on the simulated results, two correlations are formulated to describe the solid pressure-porosity relationship covering different flow regimes. But their general application needs further tests in future work.