The unique advantage of confocal microprobe Raman spectroscopy was used to study the aggregation process of tetrakis (p-sulfonatophenyl) porphyrin (TSPP) occurring at the liquid/air interface. For the low ionic strength solution, very strong Raman signals of aggregates from the liquid/air interface were detected while those were absent in the bulk solution. This is attributed to the increase of the interfacial concentration of aggregates and the assistance of the resonance Raman effect. For higher ionic strength solutions, a strong resonance Raman signal can be detected from both phases with different features which could be due to the formation of larger aggregates.