The invention discloses a biodegradable composite oxygen-barrier film and its preparation method and use. The biodegradable composite oxygen-barrier film is composed of at least two support layers and barrier layer which is located in each of the two support layers. Said support layer is selected from at least one of the following materials: polylactic acid, polybutylene succinate, polycaprolactone, poly(butylene adipate-co-terephthalate), poly(beta-hydroxybutyrate) and poly(beta-hydroxybutyrate-co-hydroxyvalerate); said barrier layers located in each of the two support layers are same or different, and the barrier layer is selected from poly(1,2-propylene carbonate) and nano-montmorillonite modified poly(1,2-propylene carbonate). The biodegradable composite oxygen-barrier film can be used as food or medicine package, and it will help to prolong shelf-life of food and medicine and the like; it can also prevent white-pollution.