Herein, a novel aptasensor was constructed for ultrasensitive detection of bisphenol A (BPA). In this method, an electrochemically mediated atom transfer radical polymerization (eATRP) signal amplification strategy was applied to BPA detection for the first time. The 5'-end modified sulfhydryl group and the 3'-end modified azide group hairpin DNA were immobilized on a gold electrode through an Au-S bond. The double-stranded DNA was formed by the hybridization of an aptamer and a single-stranded DNA partially paired with the hairpin DNA. In the presence of BPA, the aptamer combined with BPA and the single-stranded DNA was released to open the hairpin structure, making the azide groups at the 3' end exposed. Subsequently the initiator of eATRP was introduced into hairpin DNA through click chemistry reaction and eATRP was conducted for the polymerization of the electroactive probe ferrocene methyl methacrylate (FMMA). As a result, the ultrasensitive detection of BPA was realized, and the detection limit of this aptasensor was as low as 59 aM and a good selectivity was obtained in the presence of 100-fold structural analogs. The application of this aptasensor was evaluated by detecting BPA in pure water samples, and recoveries were in the range of 95.23-98.40%, holding promising applications in biological analysis.