Novel and uniform Co4S3 nanoparticles were synthesized through a two-step hydrothermal process and testified to possess intrinsic peroxidase (POx)-like activity for the first time. As a fresh POx mimic, we studied its catalytic properties, kinetic, and mechanism to catalyze the oxidation of 3, 3', 5, 5'-tetramethylbenzidine in the presence of H2O2. According to the experiments, the bactericidal mechanism is the same as that of simulated enzyme. Based on the ability of Co4S3 inducing H2O2 to express center dot O-2(-), the bactericidal rate can be as high as 100%. Besides, using the POx-like activity of Co4S3, a new off-on sensor for H2O2 and L-cysteine (L-Cys) detection is constructed. The sensor reveals a good wide linear response to H2O2 in the 40-2000 mu M with a detection limit of 18 mu M, while L-Cys in the 20-100 mu M with a detection limit of 10 mM. The proposed method also shows great stability, high selectivity, and excellent practicability. (C) 2019 Elsevier Inc. All rights reserved.