Polyether maleic acid monoester (PM) was prepared by the esterification from polyethylene glycol(PEG-200) and maleic anhydride(MA). PM was used as an allyl branching monomer to copolymerize with acrylic acid(AA) and the initiator ammonium persulfate to prepare the non-linear copolymer(PMAA) by the free radical water-solution polymerization. The structure of PM and PMAA was characterized by FT-IR, 1HNMR and 13C-NMR. Preparation of the non-linear copolymers(PMAA) additives as high exhaustion chrome-tanning auxiliary was applied to chrome-tanning process. The results indicated that the high exhaustion chrome-tanning assistant was best applying in pickling, with its weight percent 1.5%, the absorptivity of chrome was 96.57%, ensured leather surface fine and made Ts, physical mechanical performance significant increase.