In this work, a biosensor for ultrasensitive detection of glucose via electrochemically mediated atom transfer radical polymerization (eATRP) was firstly reported in the field of biosensing analysis. Firstly, 4-mercaptophenylboronic acid was immobilized onto Au electrode surface via Au-S bond to recognize glucose by producing 5-membered cyclic boronic ester. Then initiators of atom transfer radical polymerization were introduced to the electrode surface by the reaction between 2-bromoisobutyryl bromide and the remaining hydroxyl groups of glucose to produce the alkyl halide initiation site. The monomer began to graft onto the electrode surface, and an electrochemical potential was applied to activate the copper catalyst for the formation of polymeric chains which were labeled numerous electroactive probes ferrocene. The square wave voltammetry was applied to monitor electrochemical signal of quantitatively labeled ferrocene. Under optimal conditions, this strategy for ultrasensitive detection of glucose presented a good linear relationship between oxidation current of ferrocene and logarithm of glucose concentrations in the range from 1.0 nM to 10 mu M with an extremely low limit of detection of 0.32 nM (R-2 = 0.996). In addition, this strategy showed good specificity for glucose detection in physiological conditions and also showed high reliability in human serum.