A series of highly branched poly(urethane-imide) (HBPUI) were synthesized via A(2) + B-3 approach using isophorone diisocyante (IPDI), polycarbonatediol (PCDL), 3,3',4,4'-Benzophen-onetetracarboxylic dianhydride (BTDA), and poly(oxyalkylene) triamine (ATA) as materials. The structure of the products was characterized by FT-IR and C-13-NMR. The molecular weights were characterized by gel permeation chromatograph (GPC). The solution viscosity, thermal, and mechanical properties were measured by rotational rheometer, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), tensile tests, and dynamic mechanical analysis (DMA), respectively. The HBPUI showed lower viscosity than that of linear poly(urethane-imide) (LPUI), nevertheless T (g) of HBPUI was higher than that of LPUI. TGA indicated that the thermal degradation of poly(urethane-imide) occurred above 300 A degrees C, which was higher than conventional polyurethane. The tensile strength of HBPUI was obviously improved by increasing the content of BTDA and the molar ratio of [A(2)]/[B-3]. The effects of the content of BTDA and the molar ratio of [A(2)]/[B-3] on the storage modulus of the polymers were also studied.