A negative-tone hyperbranched photosensitive polyimide (HB-PSPI) based on a new triamine, 1,3,5-tris(4-aminophenoxy)benzene (TAPOB), and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) was synthesized. The photosensitive cinnamate groups were incorporated at the periphery of the polymer by the reaction of cinnamoyl chloride with the terminal phenol groups of the fully imidized hyperbranched polyimide, which was obtained via the end group modification of the anhydride-terminated hyperbranched poly(amic acid) precursor. The polymer showed good thermal property with 10 wt % loss temperature at 517 degreesC, and exhibited excellent organosolubility even in acetone and 1,1,2-trichloroethane. Photolithographic property of the polymer was examined by UV exposure. SEM analysis revealed that highly resolved patterns with a line width of 10 mum, were obtained; and well-defined line as thin as 3 mum in width could be patterned, though the line edges were jagged and rounded due to the broad molecular weight distribution.