Abstract:Caragana microphylla is one of the most widely distributed shrubs in fixed and semi-fixed sand land,semi-arid areas of northern China.Change on survival rate,plant height,osmotic regulation substances,protective enzymes and membrane permeability of C.microphylla in different sand burial depths was measured and its eco-adaption and physiological response to sand burial was studies during 2010-2011 in the Horqin Sand Land of Inner Mongolia to understand the mechanism of C.microphylla to adapt sand land environment.The results showed that:(1)The ability of C.microphylla seedlings to resist sand burial was weaker,the seedlings all died when depth of sand burial was 100% plant height.Changes of seedling survival rate were not significant at sand burial depth of 25% and 75% plant height.The plant height decreased significantly when sand burial depth was plant height 50%~75%,which show that the moderate and heavy sand burial cause the inhibition of C.microphylla growth.(2)At the buried depth of the height 25%,leaf water content increased,MDA content decreased,POD activity increased,the cell membrane was not harmed.Although the plant leaf water content decreased,MDA content increased.Due to the synergistic effects of SOD and POD to protect the cell membrane,the cell membrane is not damaged when the buried depth of the plant height was 50% and 75%.At the buried depth of the height 25%~75%,changes in the soluble sugar and proline were not significant because the sand burial stress is light and the cell membrane has not been damaged.It was concluded that C.microphylla seedlings can only withstands the partial burial by sand,all the seedlings died when subjected to completely sand burial.It was one of the main physiological mechanisms that soluble sugar and proline failed to play an effective role in osmotic adjustment process with a increase of sand burial stress.