Lonicera japonica Thunb., known as Jin Yin Hua or Japanese honeysuckle, is an herbal medicine in Asian countries. Its flowers have been used as folk medicine for clinical practice or used as food or making healthy beverage for 1500 years in China. To investigate the molecular developmental processes from L. japonica buds to flowers under UV radiation, comparative proteomics analyses of buds and flowers were performed. Fifty-four differential proteins were identified including 42 increased proteins and 12 decreased proteins. The abundance of proteins related to glycolysis, TCA/organic acid transformation, major carbohydrate metabolism, oxidative pentose phosphate, stress, secondary metabolism, hormone, and mitochondrial electron transport were increased during flower opening process under UV radiation. Six metabolites were identified and relatively quantified by LC-MS/MS in L. japonica buds and flowers. The 1,1-diphenyl-2-picrylhydrazyl assay revealed that antioxidant activity of L. japonica buds was better than that of flowers. These results suggest that UV-B radiation could induce the production of endogenous ethylene in L. japonica buds, which facilitate the buds blossom and activate the antioxidant system. Additionally, the higher content of metabolites and antioxidant capability in L. japonica buds indicates that L. japonica buds stage might be the better harvest time compared to the flower.