Rhododendron Tsinghaiense Ching grows concentrically in Jiegu mountainous country in the south of Qinghai. Its essential oil has beneficial effects in the treatment of bronchitis. According to the observation made on gas chromatography and thin layer chromatography, this ail contains at least 30 components: 4 monoterpenes; 7~9 sosquiterpenes, more than 15 oxygen-containing sesquiterpenes and traces of oxygen-containing monoterpenes and acidic; compounds. 8-cadinene and guaiol are the main components.