Abstract: Objective To compare the bacteriostasis efficacy of different irrigant to several common strain in root canal by slip diffusion method. Methods Bacterium suspension was spreaded on solid medium. Asepsis filter paper slips that contain 0.005 mL different irrigant or distilled water were placed. Specimens were cultured to determine the size of bacteriostasis -collares. Results BioPure MTAD and 1.3% sodium hypochlorite showed the maximum and minimum of bacteriostasis-collare on all strains, respectively（P<0.05）. Conclusion The excellent bacteriostasis efficacy of BioPure MTAD to experiment strain was showed by slip diffusion method.