Abstract: In order to explore molecular mechanism of soybean isoflavone synthesis influenced by UV-B radiation, isoflavone accumulation and gene expression levels in different parts of V1 stage, seedlings under UV-B treatment were investigated by HPLC and quantitative real-time PCR respectively, and genes encoding UV RESISTANCE LOCUS 8（UVR8） photoreceptor were also cloned. The accumulation of total isoflavones in leaves of soybean V1 stage was increased by 1.3 times under 8 h UV-B radiation, and daidzein, genistein improved by 15.8 and 16.5 times respectively. The transcripts of CHS and IFS exhibited obvious difference response to time after UV-B stress, and CHS11 was increased 38.4 times after 2 h treatment, and the highest expression levels of IFS1 and IFS2 increased by 4.7 and 18.3 times respectively. The coding sequences of UVR8 photoreceptor GmUVR8 a, GmUVR8 b and GmUVR8 c were cloned from soybean, the encoding protein had 74% homology in amino acids with AtUVR8, their expression levels in leaves showed significant difference, and GmUVR8 b displayed the highest transcripts among those genes. The results indicated that UV-B radiation might regulate synthesis of soybean isoflavones through multiple UVR8 light receptors which affect the expression of key enzymes in phenylpropanoid pathway.