The hyper-branched polymer with terminal carboxyl (HPAE-C) was prepared by modifying hyper-branched polymer with terminal hydroxyl with maleic anhydride. The molecular structure of HPAE-C was characterized by IR, 1H-NMR and 13C-NMR. The HPAE-C was used in the finishing process of microfiber synthetic leather, and its effect on the health properties of microfiber synthetic leather was studied. The results showed that hyper-branched polymer could improve the moisture absorption and permeability to water vapor of microfiber synthetic leather. When the dosage of HPAE-C was 8%, the permeability to water vapor and moisture absorption of microfiber synthetic leather were improved by 7% and 13%, respectively. The observation results obtained by using scanning electron microscope showed that HPAE-C could loose the fibers of synthetic leather.