An intron sequence of Poptr;CYCD1;1 from Populus trichocarpa was ligated into binary vector,pROKⅡ, to obtain the construct for gene silencing in plants. The resulting pRNAi was used to silence the exogenous fusion gene, GUS:GFP, in transgenic tobacco transformed with pCAMBIA-1303 vector. The specific sequence from GUS and GFP genes was cloned into pRNAi, respectively, and both of them reduced the expression of GUS:GFP gene. The results implied that the present pRNAi could be used to silence some gene of interest.