Abstract: Abstract: Objective To evaluate the efficacy of chlorhexidine gel (CHX), calcium hydroxide (CH) and calcium hydroxide combined with chlorhexidine (CHX+CH) as a root canal disinfection drug in root canal therapy, in order to find the ideal root canal disinfection drug and provide scientific evidence. Methods Sixty teeth with chronic apical periodontitis were randomly divided into CHX, CH and CHX+CH groups, respectively, 20 in each group. Rinse with conventional mechanical preparation was conducted respectively. CHX, CH and CHX+CH were selected, and the samples of the bacterial specimens in the root canal were sampled and cultured before and after the preparation of the root canal, and the changes in the number of bacteria in the aerobic and anaerobic bacteria were determined. The clinical efficacy of the dental seals before and after 7 days was observed and scored, and the average sealing time of the teeth was recorded. Results After the teeth of three groups were sealed, the number of aerobic and anaerobic bacteria in the root canal (the logarithmic value) was significantly lower than that before the seal (p<0.05). The bacteriological examination of aerobic and anaerobic bacteria after 7 days of root canal sealing in the three groups showed that there was no significant difference in the number of bacteria in the root canal between the CHX group and the CH group (p>0.05). However, there was a statistically significant difference in the number of the aerobic and anaerobic bacteria in the root canal between the CHX+CH group and the other two groups (p<0.05). After 7 days of root canal sealing in the three groups, the clinical scores of each group were statistically significant (p<0.05), indicating that all three root canal disinfectants had certain curative effect. In CHX group and CH group, there was no significant difference in the difference of clinical scores before and after 7 days of sealing (p>0.05), but the difference of clinical scores before and after 7 days of sealing between CHX+CH group and the other two groups was statistically significant (p<0.5). ). The three groups of teeth reached the clinical fillable requirements through different treatment time. There was no significant difference between the CHX group and the CH group (p>0.05), but the difference between the CHX+CH group and the other two groups was statistically significant (p < 0.5). Conclusion CHX, CH and CHX+CH as root canal disinfection drugs all have good curative effects on chronic apical periodontitis, and the comprehensive evaluation of antibacterial effect and clinical efficacy of CHX gel combined with CH paste are the best, which is expected to be a disinfectant with good clinical treatment effect.