To compare the postobturation pain and therapeutic effects in root canal therapy between two root canal filling materials: AH Plus and zinc oxide eugonol. Four hundred and twenty four teeth requiring root canal therapy were randomly divided into 2 groups: AH Plus ( trial group ) or zinc oxide eugonol ( control group) were used in treatment respectively. The pain intensity after treatment was evaluated by visual analogue scale. The therapeutic effects were evaluated by follow-up for 6 and 12 months. The pain intensity of trial group was significantly lower than that of the control group in 3rd and 7th day[8. 5% ( 18/212) vs. 15.6% (33/212),5.2% (11/212) vs. 14.6% (31/212),both P ＜0.05]. There were no significant differences in effictive rate between two groups after follow-up for 6 and 12 months[92. 5% ( 196/212) vs. 89. 6% ( 190/212 ) ,91.5% ( 194/212 ) vs. 88.7% ( 188/212 ), both P ＞ 0. 05]. AH Plus root canal filling paste used in root canal therapy can significantly decrease postoperative pain.