With further development of the turbofan aero-engine, the compressor intermediate duct can no longer be considered to merely perform the service function of transporting fluid from low-pressure component to high-pressure stage. Especially for the practical compressor intermediate duct with inclined uncambered struts, the high-curvature geometry, great internal pressure gradient, and strong three-dimensional effect make it extremely sensitive to the real inflow conditions, which would not be applicable to the previous research methods based on two-dimensional axisymmetric assumption. In this paper, numerical investigation was conducted about the influence of inflow conditions on a compact compressor intermediate duct with eight inclined struts and numerical approach was validated by comparison with experiment data and the computation accuracy of flow field details was studied by different grid settings. This study deeply explored the flow mechanism and aerodynamic performance about how the pre-swirl angle, inlet Mach number, and distorted total pressure effect of the compressor intermediate duct flow field. The results indicate: (1) for a compact compressor intermediate duct, the proper predication for the flow separation due to an aggressive geometry depends on the radial computing grid strongly, (2) the leeward side of the uncambered strut is extremely sensitive to the pre-swirl inflow, and the existence of backflow and exit non-uniformity is caused by the pre-swirl inflow, (3) the airflow adjacent to the casing wall is more sensitive to the inlet Mach number, whose increase will strengthen the exit non-uniformity and interaction between the strut wake and endwall boundary layer, and (4) the distorted inflow through compressor intermediate duct channel will be amplified because of the compact geometry.