Polyimide (PI) exhibits outstanding chemical and physical resistance, yet PI foam suffers from low mechanical strength, limiting its application as structural material. Organic heterogeneous reinforcement compromises its tolerance, while inorganic reinforcement reduces plasticity. This study proposed three homogeneous composite strategies, incorporating short-cut PI fibers, PI micro-powder, and non-foamable precursor powder, to enhance PI foam. The morphology and mechanical properties were characterized, and the non-foaming mechanism of ethanol-prepared precursor powder was investigated. The results demonstrate that all homogeneous composites increase the density, bending strength, and compressive strength of PI foam compared to the control group. The maximum increases reach 45.1% in bending strength and 188.6% in compressive strength. However, homogeneous compounding will damage the cell walls, resulting in a lower increase in bending strength relative to the density increase for most samples.