To　study　and　measure　the　viscosity　coefficient　of　unknown　gas,　a　simple　measuring　device　based　on　capillary　was　built.　According　to　Poiseuille＇s　law,　the　relationship　between　gas　volume　flow　and　viscosity　coefficient　was　established.　With　N2　as　the　calibration　standard　gas,　the　viscosity　coefficients　of　H2,　C02　and　synthetic　air　in　the　temperature　range　of　280　~320　K　and　the　pressure　range　of　169　~　376　kPa　were　calculated　by　measuring　the　volume　flow.　The　reliability　of　this　method　is　theoretically　analyzed,　and　the　results　are　compared　with　the　viscosity　coefficient　in　NIST　database.　The　relative　error　rate　of　this　method　is　in　the　range　of　[-　1.　109%　,1.　779%]　when　the　differential　pressure　is　in　the　range　of　103　~206　kPa.　©　2024　Chinese　Society　for　Measurement.　All　rights　reserved.