Abstract: [Objective] In order to understand the influence of water stress on plant layer of epicuticular wax and its component contents and the relationship between the leaf layer of epicuticular wax and plant drought resistance.[Method] The paper studied the variation of flag leaf and layer of flag leaf epicuticular wax content in two barley with strong drought resistance and 2 varieties with weak drought resistance.[Result] The results showed that the epicuticular wax content of barley leaves under drought stress increased and that of drought tolerant cultivars increased more than that of drought sensitive cultivars,and after drought stress,the main physiological parameters of photosynthesis were decreased.The main components of epicuticular wax of barley leaves were alcohols,alkanes,acids,aldehydes,esters and ketones;the increase of epicuticular wax of barley leaves under drought stress was mainly due to the increase of alcohols,esters and ketones while the increase of alkanes was not obvious;net photosynthetic rate of barley leaves was positively correlated with the alcohols content and negatively correlated with the alkanes content,indicating that alcohols and alkanes as the main components of epicuticular wax of barley leaves had significant auxo-action to photosynthesis;stomatal conductance was negatively correlated with total wax content and alcohols content.[Conclusion] The content of alcohols,esters and ketones of epicuticular wax in barley leaf will be increased under drought stress condition,then the photosynthetic characteristics is regulated by wax components to maintain a high photosynthetic rate,which can improve the drought tolerance of plants.