Abstract: Taking the tube seedlings of four Rhododendron cultivars ‘Cosmopolitan’‘Lord Roberts’ ‘Scintillation’ and ‘Polaris’ as test materials, the effects of five pH levels of culture media on the growth of test tube seedlings of Rhododendron were studied by using the method of alkaline tolerance evaluation in vitro,through observation of morphological indicators（alkaline damage index, plant height growth, bud proliferation number） and determination of physiological indicators（soluble sugar content, superoxide dismutase（SOD） activity）,in order to provide reference for indoor evaluation of alkaline resistance of Rhododendrons.The results showed that among the four Rhododendron cultivars, ‘Cosmopolitan’ had the strongest alkali resistance with an alkali damage index of 13 at pH 8.9,it′s plant height growth was significantly higher than other treatments at pH 8.1; next was ‘Lord Roberts’,with an alkali damage index of 62 at pH 8.9 and a significantly higher plant height growth at pH 4.8 and 7.0 compared to other treatments; ‘Scintillation’ and ‘Polaris’ were the least alkali resistant, with an alkali damage index of 97 and 100 at pH 8.9,respectively. Except for the treatment of pH 8.9,there was no significant difference in bud proliferation coefficient for the same variety at other pH levels. At pH 7.0,the SOD activity of ‘Cosmopolitan’ and ‘Polaris’ began to significantly decrease, while at pH 5.9,the activity of SOD began to significantly decrease in ‘Scintillation’,since pH 8.1,the SOD activity of ‘Lord Roberts’ had been significantly lower than at pH 4.8 and 5.9. Four Rhododendron cultivars have the highest soluble sugar content in response to increasing alkaline stress at pH 8.1-8.9.