Hyperbranched polyurethanes with various lengths of linear segments between two branching points were synthesized by an A2 + B3 polymerization approach, where A2 is an aliphatic diisocyanate and B3 is a triol with three poly(ethylene glycol)–polycaprolactone diblock chains. The influences of the A2/B3 monomer ratio and the segment length on the gel point and thermal properties of the polymers were investigated. Crystallization behavior of the hyperbranched polymers can be controlled by tuning the segment length between two branching points. Surface restructuring is observed after oxygen plasma treatment because of the temperature effect and preferential etching effect. The effects of oxygen plasma treatment on the surface morphology, surface energy, surface chemical properties and postsurgical anti-adhesion properties of hyperbranched polymer films were studied.