The invention relates to the technical field of electrochemical detection, and in particular relates to an electrochemical sensor for detecting tyrosine as well as a preparation method and application thereof. The electrochemical sensor adopts a chemically modified electrode for detecting the tyrosine as a working electrode, Ag-AgCl as a reference electrode, and a platinum wire electrode as an auxiliary electrode. An electrode test system is connected with an electrochemical working station to form the electrochemical sensor for detecting the tyrosine after the electrode test system is assembled by utilizing a three-electrode method. The chemically modified electrode or the electrochemical sensor for quantitatively detecting the tyrosine has extremely low detection limit and a wider detection range as well as good stability, anti-interference ability and reproducibility.