In this experiment, Dendranthema indicum var. aromaticum was used as material and five treatments of 0 (CK), 1, 3, 5 and 7 d radiation with UV–B were designed to study the effect of ultraviolet radiation on the morphology, density of the trichomes and the surface secretion of leaves. The results showed that glandular trichomes of UV–B treatment appeared irregular depressions in the middle, or even distortions. The apical cells of “T” shape hairs with non–glandular ruptured or even fallen off. As the radiation days increased, the densities of glandular trichomes and “T” shape hairs with non–glandular showed a trend of first increased then decreased. Their densities were the highest on the lower epidermis of leaves in the treatment of 1 d, which the glandular trichomes numbers on the tip, middle and base of leaf were 16.00, 13.67 and 18.67 respectively in each vision field and “T” shape hairs with non–glandular numbers were 43.84 in each vision field. The relative content of leaf surface secretion of alpha pinene and alpha cubebene did not change significantly, while cadinene and 1–caryophyllene were higher volatility and reached the highest level of 19.45% and 14.71% with 3 d radiation. Relative percentage content of camphor, alcohols and ketones presented a trend of first increased then decreased with the increase of radiation days. Their content reached largest in 1 d or 3 d and dropped to the lowest in 7 d.