In order to improve the calibration ability of the micro gas flow and expand the lower limit of the flow calibration range, the passive piston glass volume tube master standard was used as the research object, and a method of using a laser interferometer to measure the displacement of the piston in real time to calculate the standard flow was proposed. This method extended the lower limit of the flow range from 1 mL/min to 0.01 mL/min. The research performed flow repeatability test and standard flow uncertainty analysis. The results show that the standard has good measurement performance in the extended micro flow range, meets the traceability calibration requirements, and achieves a technological breakthrough in micro-upgrading micro gas flow calibration.