A novel catalyst preparation method is developed by solid-state interaction between ZnCl2 and NaY zeolite under microwave irradiation. The solid-state interaction is investigated by powder X-ray diffraction, FT-IR spectroscopy, and by testing the catalytic properties in the Diels-Alder reaction of myrcene and acrolein. XRD patterns indicate that ZnCl2 can disperse completely on the surface of NaY zeolite at the ZnCl2 loading less than 2.75 mmol g(-1). Fr-IR spectra of pyridine adsorption on catalyst show that Lewis acid sites are the predominant acid sites. The catalyst of ZnCl2/NaY prepared by the treatment of microwave irradiation is proved to be an effective heterogeneous catalyst for high regioselective Diels-Alder reaction of myrcene and acrolein. The catalytic activity and the regioselectivity of p/m strongly depend on the ZnCl2 loading. With an increase of the ZnCl2 loading up to 0.92 mmol g(-1), the activity and selectivity increase a little. In this case, the active site is deduced from the zinc ion species formed by solid-state ion exchange. The Lewis acid sites are too weak to catalyze efficiently the Diels-Alder reaction. Keeping an increase of ZnCl2 loading from 0.92 mmol g(-1) to 1.84 mmol g(-1), the activity and the regioselctivity of p/m increased markedly due to the formation of new zinc ion species of -O-Zn-Cl as Lewis acid sites on NaY zeolite. The catalysts leached with a mixture solvent of acrolein and dichloromethane show little loss of catalytic activity and selectivity. Thanks to the possibility of simple and safe handling of the ZnCl2/NaY and to its easy separation from organic products, it becomes an alternative Lewis acid catalyst for the Diels-Alder reaction to homogeneous Lewis acids. (C) 2003 Elsevier B.V. All rights reserved.