This paper presents colorimetric determination of Hg(II) based on MoS2 nanosheets with peroxidase mimics activity. The structure of the this sensor by the peroxidase mimic activity material of MoS2 nanosheets with TMB (Tetramethylbenzidine) solution, the colorimetric detection target of Hg(II) is determined by on-off mechanism using biomolecule of cysteine. The MoS2 nanosheets evaluated by X-ray diffraction, FT-IR and SEM image, confirms formation of a flower like structure. Our results shows that a simple colorimetric detection using peroxidase mimic mechanism can be used to MoS2 nanosheets and determine the Hg(II) in aqueous solution with high sensitivity (10 nM) comparable to those of other nanomaterials. The result suggests that MoS2 nanosheets is a promising new and simple colorimetric sensor for applications in environmental and biological applications.