The invention discloses 3-aryl coumarin derivatives (I) and (II) and a preparation method thereof and belongs to the field of organic chemistry. According to the method, a substituent coumarin derivative and substituent arylboronic acid are used as raw materials and changed into a solvent with acetic acid under the catalysis of Mn(OAc)3 to synthesize the 3-aryl coumarin derivatives. The synthetic method has the advantages that the raw materials are low in price and easy to get, reaction conditions are mild, the yield is high, operation is convenient, and industrial production is facilitated. The derivatives have potential application in the fields of materials, chemical industry, medicine and the like. A new way is provided for synthesis of the 3-aryl coumarin derivatives. (Please see the description for the formulas I and II).