The dust particle counter is a prescribed measuring instrument that needs to be calibrated regularly every year according to the metrological verification regulations. Because after a period of use, the optical and detection systems of the dust particle counter will undergo changes, such as aging of the light source, decreased luminous efficiency or focusing misalignment, and lens contamination, resulting in changes in the overall conversion sensitivity of the machine. The calibration of a dust particle counter involves adjusting all aspects of the instrument to achieve optimal working conditions.