Dimocarpus longan(Lour.) is rich in flavonoids and other secondary metabolites, and has important nutritional and medicinal values. Light quality could regulate flavonoids in the longan embryonic callus(ECs). However,the effect of red and blue composit light on the longan ECs has not been reported.Therefore,the effects of different red-blue composite light ratio on the growth status and flavonoid metabolites content of longan ECs were investigated,and the expression profiles of DlCHS,DlLAR and DlHY5 were analyzed.The results showed that the growth rates of longan ECs were highest under the light condition(red∶blue=1∶9,2∶8),up to 1 107.50% and 1 130.0%,respectively.The contents of total flavonoids and epicatechin reached the highest value under the light condition(red∶blue=1∶9),up to 12.49 mg/g and 2 187.54 μg/g,respectively.When the red-blue composite light ratio was 5∶5 and 3∶7,the DlCHS and DlLAR gene expression levels were the highest,while the DlHY5 expression level was the highest when the red-blue composite light ratio was 1∶9.The red-blue composite light was beneficial to the synthesis of flavonoids and epicatechin in longan ECs,and the synthesis of secondary metabolites were improved with the increase of the ratio of blue light.