A novel method to intensify the foam fractionation process by operating the column under reduced pressure was reported in this paper. It was found that a poorer foam stability, a bigger mean bubble size and a wider bubble size distribution in the foam layer, a less upward liquid flux and volumetric liquid fraction at the top of the foam layer, and a higher enrichment ratio but a lower mass recovery of the foam fractionation process were obtained under reduced pressures compared to the ones under atmospheric pressure. The most important effect of the reduced pressure on the foam layer during the foam fractionation process is the encouraged bubble coalescence process which was exhibited by those unusual foam properties discussed above. The limitations of this new method were also discussed.