Abstract: To explore the reasons of color change in AmRosea1 overexpressed 84K poplar（Populus alba×P.glandulosa ’84K’） caused by light signal,the wild type and AmRosea1 overexpressed 84K poplar were used as the materials.The anthocyanin content,chlorophyll content,soluble sugar content and POD activity under LED light,natural light,LED red light,LED blue light,and LED red and blue light treatment were measured,and the changes of physiological indexes of wild type and transgenic lines under different optical signal were determined respectively.The results showed that under different light intensities,compared with the LED light treatment,the leaves of the transgenic lines turned red,and the anthocyanin content and soluble sugar content increased,and the chlorophyll content and POD activity decreased under natural light.After 30 days of different light treatments,the LED red-blue light treatment that the antho-cyanin content increased,the soluble sugar content and POD activity decreased,and the chlorophyll content decreased slightly under LED red and blue light induction compared with LED red and blue light.Based on the experimental results,it was speculated that strong light and red and blue light quality might activate the anthocyanin biosynthesis pathway and accumulate a large amount of anthocyanins in AmRosea1 overexpressed 84K poplar,which in turn the leaves turned red.