Abstract: In this Research, a special floral bud development phase was discovered in Rhododendron mucronatum, which was the elogation axillary floral buds in autumn. Farther, the results showed that higher light intensity (over 40%), opitimal air temperature(25-26°C) and plentiful rainfall where the main facters to cause the elongation. Based on these facts, rhododondron mucronatum could be considered as one of the sun plants.