The invention discloses a synthesis method for a coumarins compound. The structural formula is shown in the specification, wherein R1 is selected from one or more of -H, -CH3, -OCH3, -F, -Cl, -Br, -OH, -NO2 and N(CH2CH3)2 and R2 is selected from one of -H, -CH3 or CH2CH3. According to the invention, a 2-hydroxy cinnamate compound is directly utilized as a raw material and the coumarins compound is synthesized in one step under the catalytic effect of visible light. Compared with the present synthesis method, the synthesis method for the coumarins compound disclosed by the invention has the characteristics of simple method, mild condition and high yield; the reaction is carried out under normal temperature; and the visible light is utilized as a reaction energy source and is green and pollution-free.