Abstract: Esterification reactions of dicarboxyl-capped polypropylene(PP) with methoxy polyethylene glycol (MPEG) were conducted to prepare block copolymers of polypropylene and polyethylene glycol (PEG-b-PP-b-PEG) with different block chain molecular weights. PEG-b-PP-b-PEG was blended with polypropylene films, as macromolecular surface modifiers, to prepare blend films. Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR), Contact Angle Tester and Atomic Force Microscope (AFM) were used to characterize surface composition and properties of the blend films. Results showed that PEG-b-PP-b-PEG could improve the surface hydrophilicity and polarity of the PP films, and the enhancement of surface properties was dependent on the mass fraction of PEG chain segments in the films and the block chain molecular weight of PEG-b-PP-b-PEG. With the increase of PEG segment chains mass fraction in the film, water contact angle of the films decreased, and surface free energy increased. As the chain molecular weight of PEG block and/or PP block in PEG-b-PP-b-PEG decreased, water contact angle of the films also decreased, and surface free energy increased too. When molecular weights of both PEG block and PP block in PEG-b-PP-b-PEG were around 1 000, an enhanced surface hydrophilicity modification effect was obtained.