The invention belongs to atmospheric radiation environment monitoring and nuclear facility safety running monitoring systems and methods, and particularly relates to an atmospheric xenon enrichment and purification method and device and a method for preparing a carbon molecular sieve. The atmospheric xenon enrichment and purification method mainly includes the steps of air pretreatment, three-level concentration, separation and purification, sample preparation and online stable xenon detection. M hollow fiber nitrogen-enriched membrane components of the same type and/or different types are connected in series and/or in parallel for separation in the air pretreatment process. The carbon molecular sieve is used as an adsorbent in the step of separation and purification. The problem of low enrichment efficiency of an existing atmospheric xenon enrichment and purification method and device is solved, the quantity of xenon acquired in 24 hours by the system is not smaller than 10mL, xenon volume-by-volume concentration is not lower than 30%, and quantitative uncertainty of stable xenon is less than 10%.