A simple and recyclable catalytic system for direct arylation of heteroarenes via C–H bond activation was developed with a relatively inexpensive RuCl₃·xH₂O as a catalyst and PEG-400 as a green medium without any additive or ligand. This system not only showed excellent functional group compatibility, but also the ratio of mono- to diarylated product was easily regulated by varying the reaction conditions. Moreover, this transformation could proceed under air and be easily scaled up to gram-scale in a low catalyst loading of 0.3 mol%. Particularly, a good yield of 85% was obtained after this catalyst was recycled six times.