BiDy composite oxide nanoflakes with the thickness of about 50 nm were synthesized by one-step hydrothermal method. The electrodes modified with BiDy composite oxide nanoflakes exhibit superior electrochemical behavior for detecting L-cysteine using cyclic voltammetry (CV) method. The impact of scan rate, electrolyte, and concentration of L-cysteine for electrochemical behaviors were investigated. A pair of strong quasi-reversible CV peaks are observed at +0.03 V (cvp1) and –0.69 V (cvp1′) with peak current of 171.2 μA and 171.3 μA, respectively for the BiDy composite oxide nanoflake-modified GCE in 0.1 M KCl and 2 mM L-cysteine solution. GCE modified with the BiDy composite oxide nanoflakes displays broad range of linearity (0.001-2 mM) and low detection limit (0.29 μM) for L-cysteine. Using a hydrothermal approach as a synthesis technique for nanoflakes, as well as a facile and sensitive electro-chemical sensor based the nanoflakes was developed to detect L-cysteine, makes it a promising approach for practical application.