The experiment was done within -2014 in plant physiology lab.of agriculture faculty of Tishreen University for estimation of high temperature stress toleration of citrus leaves in three varietis(Citrus Unshiu , Meyer Lemon,Citrus SinensisWashington). Many random samples of leaves were gathered from the foliage of the examined categories whereas tha average of the taken leaves was 200 from the whole sides for each one tree from the branches which are one year old . which were put for limited duration in a water bath about many different degrees of temperature then they were put in water and then in a solution of HCL acid . Many references were studied of containing :non spotting on leaves ,which means they are un harmed,simple spotting,the spotting of more than half of the leaves area,the perfect leaves spotting. Studied temperature were as the following :40-50-60-70-80.Each one of this mentiond temperature,40 leaves were used .The statistics analys were done with the way of Genstat 12,for the comparison between averages for the sake of calculating the least significant difference at the guidance level :5% . Studies showed that Satsuma leaves are the most toleration for high temperature,next Citrus SinensisWashington is less than Satsuma.At last Meyer Lemon was the least .