Accurate determination of cellular membrane fusion is essential to identify the nature of biological phenomena such as neurotransmitters transmitting across a synapse from one neuron to another, sperm and egg fusing, fusion proteins play an important role in these processes, but the first step of fusion(membranes aggregation) is no very clear.In this study, we proposed a novel method to deduce the membrane aggregation processes, generated in sum frequency generation vibrational spectroscopy (SFG-VS).By investigating the influence of peptide concentration on the symmetric vibration signals of phospholipid bilayer at the water/CaF2 surface, the intensity ratio about the symmetric vibration signals of phospholipid between peptide induced bilayer and monolayer has been observed which is more than 10.It implies that the lipid has aggregated.