Abstract: To study the light signaling process in anthocyanin synthesis, by means of physiological, histological method and spectrophotometry, the effete of light on anthocyanin synthesis, location of anthocyanin synthesis and the action of NO and H₂O₂ in light-induced anthocyanin synthesis were measured in mung bean hypocotyl. The results show that light induced anthocyanin synthesis, and the effect was time-dependent. The location of anthocyanin synthesis was parenchyma cells under epidermis in hypocotyl of mung bean. Further, lightinduced anthocyanin synthesis was largely prevented by≥10 mmol/L NO synthase inhibitor L-NAME,≥300μmol/L nitrate reductase inhibitor Na2WO4,≥300μmol/L NO scavenger hemoglobin (Hb),≥3μmol/L DPI, an inhibitor of the H₂O₂-generating enzyme NADPH oxidase,≥10 mmol/L Vc, an important reducing substrate for H₂O₂ removal, or≥200 units/mL H₂O₂ scavenging enzyme CAT, indicating that NO and H₂O₂, as intermediate signal molecule, mediated light-induced anthocyanin synthesis.