Recent findings have thrust poly ADP (ADP: adenosine diphosphate)-ribose polymerase-1 (PARP-1) into the limelight as potential chemotherapeutic target because it is closely related to the development of tumor. So, studies on its detection and inhibitors evaluation have attracted more attention. It is interesting that poly (ADP-ribose) (PAR), the catalytic product of PARP-1 in the existence of nicotinamide adenine dinucleotide (NAD+), possess twice charge density of DNA strands. PAR contain 200 units, i.e., about 400bp bases, and multiple branched strands. So, plentiful negative charges on PAR supplied exquisite environment for PANI deposition, which was triggered by horseradish peroxidase (HRP). Because of the unique electrochemical property of PANI, ultrasensitive electrochemical detection of PARP-1 was proposed. Under optimum conditions, DPV intensity linearly increased with the increment of PARP-1 in the range of 0.005-1.0 U. The detection limit was 0.002 U, which was comparable or more sensitive than that obtained from previously reported strategies.