Abstract: Objective：To compare the effects of Protaper Next and Wave One root canal preparation system on postoperative pain after root canal treatment. Methods：A total of 234 patients who met the inclusion criteria were randomly assigned to groups A and B. Group A was the Protaper Next group (n=112), and group B was the Wave One group (n=122). Theincidenceanddegreeofpostoperativepainwasrecordedafter24h.According to the pain assessment criteria of Cerorgopoulou, the pain of teeth with different root canal number and pulp vitality were compared between the two groups after operation. Results：There was no statistical difference between groups A and B, but there was a statistically significant difference in postoperativepain on different dental pulp activities (P=0.0002). Conclusions：The postoperative pain status of Protaper Next and Wave One is not a basis for choosing a root canal preparation instrument, whereasthe patient’s pulp activity has an important influence on postoperative pain.