In this paper, a novel polymeric antistatic agent, TMQ, with excellent antistatic properties, low cost, and good compatibility with polypropylene (PP), was prepared from isopentenyl polyoxyethylene ether (TPEG), maleic anhydride (MAH) and homemade quaternary ammonium salt (QAS). The structure is characterized using FTIR and 1H NMR. How the addition of TMQ and the molar ratio of TPEG, QAS, and MAH affect the antistatic, mechanical, and crystalline properties of PP are investigated. The results show that as the feed ratio of TPEG, MAH and QAS is TPEG:MAH:QAS = 1:8:8, the modified PP displays the best overall performances. Further exploring finds out when TMQ is added at 15 wt%, the surface resistivity of PP reduces to 6.78 × 109 Ω/sq and the volume resistivity of PP reduces to 7.9 × 109 Ω cm−1, the notched impact strength and melt index improve by 357% and 991%, respectively, while the tensile strength decreases by 38.6% compared with that of pure PP. Besides, the crystal study shows after TMQ is added, the crystallinity of PP reduces, the melt peak temperature remains essentially unchanged, and the crystallization peak temperature increases slightly. The material has excellent antistatic resistance to washing and durability, and the changes in relative humidity have little effect on its antistatic properties.