ObjectiveThe aim of this study was to evaluate the apical sealing ability of iRoot SP root canal sealer using dye penetration test on the simulated root canals.MethodsEighty-eight simulate root canals were randomly divided into four test groups（20 canals each）and one positive control group（8 canals）.Group A1 specimens were obturated with iRoot SP using single-cone technique.Group A2 specimens were obturated with iRoot SP using warm vertical compaction technique.Group A3 specimens were obturated with AH-plus using single-cone technique.Group A4 specimens were obturated with AH-plus using warm vertical compaction technique.The simulate root canals were put into methylene blue and the apical microleakage was evaluated by dye penetration method.Linear and quantitative dye penetration were measured and analyzed.ResultsThe value of group A1 was greater than group A2, there was significant difference between two groups（P<0.01); The value of group A2 was greater than group A4, there was a significant difference between the two groups（P<0.01).ConclusionThe apical sealing ability in vitro of iRoot SP is less than AH plus.When iRoot SP is used to seal the canals, the effect of warm vertical compaction technique is better than single-cone technique.