Although tremendous efforts have been devoted to providing specificity for molecular sensors, most of methods focus on structural variation of the binding or reaction site to improve selectivity. Herein, we report a new approach that a chemical probe, possessing a mediocre recognition site, can successfully discriminate a target among various interferences only with electrochemical manipulation. The dicyanovinyl group of the synthetic probe (1) was expected to react not only with a cyanide anion (CN^-), but also with sulfides and biothiols to produce similar adducts. However, the binding adduct (1-CN^-) between 1 and CN^- has significantly different energy levels to be only able to undergo electrochemical oxidation under ~1.0 V (vs. Ag/AgCl), which eventually generated strong electrochemiluminescence (ECL). The ECL emission from 1-CN^- can successfully discriminate CN^- without significant interferences from other analytes including sulfides and biothiols, and exhibited a linear correlation (R₂ = 0.994) with CN^- concentrations in a range of 0‒400 μM (LOD = 0.3 μM, n = 5). Energy density calculations were utilized to design the entire strategy, and electrochemical studies supported the mechanism of CN^- discrimination. Our approach was finally applied to direct trace analysis of CN^- in tab water (≥ 1 μM), and showed excellent performance suggesting a new, versatile, and rapid determination method for molecular toxins in real samples.