• Core-shell nanowires of Cu@PBA was in-situ fabricated via a novel electrodeposition route. • Cu provided high electrocatalysis and electron transfer rate and was protected by PBA. • The as-prepared AA sensor showed an ultra-low detection limit and ultra-wide linear range. • Excellent anti-interference ability and stability support its practical applications. Ascorbic acid (AA) is an important deoxidizer contained in food, drink and medicine. However, existing detection methods are time-consuming and complex to industrial production and quality testing. Here, we proposed a core–shell nanowires constructed electrochemical sensor to achieve the highly sensitive and selective recognition of AA with a long-term reusability. Cu nanowires with 30 nm diameter were served as both structure skeleton and reactant to induce in-situ growth of Cu-Fe Prussian blue layer with 10 nm thickness covering its surface to form a core–shell architecture. This nanocomposite couples advances of Cu and Prussian blue to possess both high electrocatalysis and conductivity. The as-prepared sensor shows an excellent sensitivity with an ultrawide linear range, together with the remarkable reusable ability during 30 days with 300 times of repetitive detection. Used for four kinds of juice and bear as real samples, this sensor can accurately reported AA concentration within 5 s.