High-Speed Centrifugal Compaction Process (HCP) is a wet compacting method, in which powders are compacted under a huge centrifugal force. The HCP was well applied to small alumina specimens, but the compact easily cracked when we applied the HCP to other materials. In the present study we clarify the mechanism that introduces such cracks. Firstly, we observed HCP alumina, dyeing with iron oxide powder or by the Immersion Liquid Technique, and found that there was a kind of flow pattern generated during the HCP. A simple simulation also revealed that the formation of such a flow pattern was related to the Colioli’s force in the centrifugal field, and therefore was hard to suppress. Nonetheless, the actual introduction of inhomogeneity along the flow was largely affected by another factor. Die releasing oil was dragged in the flows and formed low density regions along the flow.