The invention discloses a method for preparing monodisperse near-infrared quantum dots, comprising the following steps: using diethyl dithiocarbamate as a monophyletic reaction precursor; carrying out pyrolytic reaction in mixed solution of surface active agent with high boiling point and different coordination properties and selecting silver sulfide as the target product to be prepared to obtainquantum dots with excellent dispersibility, low toxicity and near-infrared emitted light property. The method of the invention features in mild reaction conditions, simple operation, safety and good repeatability, eliminates toxicity caused by using the traditional quantum dots and provides necessary and provides necessary preparations for studies of application of the quantum dots as a fluorescence label indicator to a near-infrared biomarker and to the image formation field.