Objective To investigate the clinical effect of root canal disinfection with calcium hydroxides dressing respectively in four different vehicles(physiological saline, iodine glycerin, camphorated para-monochlorophenol and camphorated para -monochlorophenol/iodine glycerin), in order to provide reference for clinical root canal treatment. Methods To divide 80 teeth of single-root canal teeth having chronic apical periodontitis randomly into four groups according to the vehicles(physiological saline, iodine glycerin, camphorated para-monochlorophenol and camphorated para-monochlorophenol/iodine glycerin), observing the clinical effect after 7 days, bacterial colony numbers of root canal contents before and 7 days after calcium hydroxides dressing, clinical duration of root canal treatment. Results The camphorated para-monochlorophenol/iodine glycerin is the most effective vehicle of calcium hydroxides among four groups(P0.05). Conclusions This research suggested that camphorated paramonochlorophenol/ iodine glycerin is the most clinically effective vehicle of calcium hydroxides for root canal disinfection during physiological saline, iodine glycerin, camphorated para-monochlorophenol and camphorated paramonochlororophenol/ iodine glycerin.