A novel approach to hyperbranched polymers is presented in this work. Hyperbranched polyesters with a large amount of terminal hydroxyl groups are prepared by a one-pot synthesis from commercially available AB-type and CDn-type monomers (n greater than or equal to 2). In this paper, Michael addition of diethanolamine (CD2) or N-methyl-D-glucamine (CD5) to methyl acrylate (AB) generates dominantly AD(n)-type intermediates. Further self-condensation of intermediates at higher temperature and in the presence of catalyst gives hyperbranched polyesters. Because of the tertiary amino groups in the backbone and the hydroxyl groups in the linear and terminal units, the resulting hyperbranched polyester is highly soluble in water. Furthermore, the hyperbranched polymer is degradable because of its ester units. So, the water-soluble hyperbranched polyesters might be applied as a novel material for drug delivery.