This paper reports the effect of cell structure and air flow on oil absorption of highly oil absorptive polyurethane foam (ON-PUR) which is suitable for on-site foaming. We have developed ON-PUR for highly oil absorbing polyurethane foam with very reactive recipe. ON-PUR was synthesized with mixing polyol, water, additives and polymeric diphenylmethane diisocyanate (P-MDI) by a high pressure foaming machine. Density, air flow, oil absorption of the foam, and cell structure by microscope were measured. From the results it was found that the air flow of the foam increased by crushing, and the oil absorption of the foam sharply increased in a narrow range (from 0.1 to 0.8 ft3/min: SCFM). The increase is supposed to be due to the decrease of closed cell structure by crushing treatment.