The aggregation behavior of surfactants in crowding consisted of polyethylene glycol (PEG) was investigated by using low-field nuclear magnetic resonance(LF-NMR).The data of different surfactant-PEG systems obtained from the CPMG sequence′s echo peaks and those inversed and fitted revealed that the molecular masses and concentrations of different PEG solutions could be distinguished by using low field nuclear magnetic resonance.The formation of micelles in PEG solutions with high concentration was observed，but it was not favorable for the observation of the process of micellization in the PEG solutions with low concentration.The existing of NaCl had obvious effect on the ionic surfactants system，but had hardly effect on the nonionic surfactants system.This research enriches the application of LF-NMR technology in the characterization of the process of micellization of surfactants and has a directive significance for understanding the self-assembly behavior and function of molecules in biological systems.