It was well known that the co-complexing agents (co-CAs) were much important for preparation of double-metal cyanide (DMC) complexes and its catalytic performance for copolymerization of CO2 and propylene oxide (PO). In this work, many different Co-Zn DMCs were prepared via modulating chain length of polyethylene glycol (PEG, co-CAs), and used to catalyze copolymerization of CO2 and PO. Many technologies, such as XRD, FT-IR, SEM, BET, TG, were applied to characterize these DMC catalysts. The results indicated the chain length of PEG had significantly influenced on the structure, intrinsic nature and morphology of DMC. The co-CAs PEG can stabilize the particles of DMC and induce the DMC grow preferably into the crystallinity of monoclinic phase and morphology of nano-sheets. Moreover, the co-CAs PEG can decline the interaction of C≡N and Co or Zn. All the results caused that DMC-PEG catalyst had higher CO2 content, narrow PDI and moderate catalytic efficiency, compared with DMC-NONE prepared without co-CAs. In all DMC-PEG catalysts, DMC-PEG 4000 owned the best catalytic performance. It’s catalytic efficiency, PDI and CO2 content were 4725 g-polymer/g-Zn, 2.28 0.381, respectively.