Abstract: Air sampler is an important measuring instrument for environmental monitoring. With the rapid development of environmental protection industry, the direct-reading air sampler has been widely used.The current verification regulation JJG 956 "Air sampler" is only applicable when the standard apparatus is soap film flowmeter, whereas it is not applicable to the air sampler whose meter is a rotameter or the flow direct-reading type air sampler. Meanwhile, the corresponding standard meters are also developing rapidly and more results showed that the laminar differential pressure mass flowmeter has more advantages than the soap film flowmeter in the regulation. It can not only improve calibration efficiency, but also realize automatic calibration or even remote calibration. In this paper, the laminar flow differential pressure mass flowmeter calibration method of flow direct-reading type of air sampler was studied. The mathematical model of flow rate and relative indication error used in the calibration condition was proposed, and the uncertainty of indication error was also analyzed in detail. In addition, the evaluation example was given to prove the feasibility of the method of calibration of direct-reading type of air sampler.