Abstract: The widespread use of low-flow-rate separators in particulate matter monitoring has highlighted a need for traceable calibration. This study focuses on developing calibration equipment for variable flow rate separators. By designing various aerosol atomizing nozzles and incorporating cyclone mixing and isokinetic sampling techniques, the calibration equipment was developed for PM_2.5/PM₁₀ separators operating at flow rates ranging from 1 to 16.7 L/min. The equipment addresses several technical challenges associated with flow rate variations during calibration. The deviation between the actual and working flow rates is within ±1%, and the expanded uncertainty of the D_a50 calibration results is better than 3% (k=2), meeting both domestic and international standards.