Industry wastewater without purification treatment might contain heavy metal ions (HMIs), and the HMIs in water can induce various diseases regional outbreaks. It is necessary to monitor trace heavy metal ions in water samples. Herein, a covalent‐organic frameworks (COFs), COFBTLP‐1, is synthesized via a solvothermal reaction between 1,3,5‐triformylbenzene and 2,5‐diamino‐1,4‐benzenedithiol dihydrochloride. Two‐dimensional (2D) COFs nanosheets can be easily ultrasonically peeled from the bulk COFs. The COFs nanosheets were porous and flexible. And there are 24 metal ions adsorption sites on every cyclical structure of the COFs, provided by 12 S atoms and 12 N atoms on it. The 2D COFs nanosheets can be directly modified on the glassy carbon electrode without adhesive reagent and conductive reagent. The modified electrode shows high accuracy, high sensitivity, and low limit of detection for the simultaneous determination of four kinds of HMIs, Cd2+, Cu2+ Pb2+, and Hg2+.