Abstract: An efficient cyclotrimerization of terminal alkynes in poly(ethylene glycol)-400(PEG-400) has been developed.In the presence of PdCl2(0.04 mol),CuCl2(1 mmol) and PEG-400(1.5 g),a variety of terminal alkynes(1 mmol) underwent cyclotrimerization smoothly and formed regio-selectively the corresponding benzene derivates with good yield.It is worth while to note that the reaction was conducted under environment friendly conditions,and the catalyst could be properly recycled.