Abstract: Novel liquid composites of polyester/cellulose evenly dispersed in aqueous phase were prepared by blending polyethylene glycol (PEG) modified poly(butylene succinate) (PEG/PBS) and modified cellulose carboxymethylcellulose (CMC) and hydroxyethyl cellulose (HEC) respectively. The interaction mechanism of liquid composites was investigated by molecular simulation technology. The results show that the desired structure of PEG/PBS copolymer is successfully achieved by ¹H-NMR. Molecular dynamics simulation displays that the polarity and flexibility of copolymer chain have been effectively improved by the modification on double helix structure of PBS with PEG. The introduction of PEG changes the structure regularity. As a consequence, the compatibility between it and cellulose derivatives is improved. The analysis on energy distribution of composites indicates that strong hydrogen bonding and Van der Waals interaction exist between ether and ester group of PEG/PBS and hydroxyl groups of cellulose derivatives. These results have been explained by the deviation of absorption peak frequency on functional groups (such as OH, -OCO-, -COOH and -C-O-C-) in FTIR spectra, the change of surface interfacial morphologies in SEM photographs and the content change of C and O elements in EDS spectrum. The results show that the interaction is produced between functional groups of PBS, etherification PEG/PBS and CMC. And the interaction is improved after etherification modification. The transmittance of composites increases from 50% to more than 70%, the thermal stabilities and flexibility are also enhanced which verifies the results of molecular simulation.