Objective The purpose of this study was to investigate the differences in the anti cyclic fatigue perfor-mance of Woride KS(WKS),Proteper Gold(PTG),and Hyflex CM(HCM)nickel titanium instruments with different tip diameters in curved root canal models,and to provide reference for the targeted selection of suitable nickel titanium in-struments in clinical preparation of curved root canals.Methods Three kinds of new nickel titanium files with 20#and 25#(0.20 mm and 0.25 mm)tip diameters were selected,including WKS(20/0.06),WKS(25/0.06),PTG(20/0.07),PTG(25/0.08),HCM(20/0.06),and HCM(25/0.06),each with 20 files.According to the recommended speed and torque of the motor,the anti cycle fatigue performance of the nickel titanium file was tested in 30° and 60° stainless steel root canal models.The time from rotation to fatigue fracture(TTF)of the nickel titanium file was recorded with a camera and timer,and the fragment length(FL)was measured and recorded with a Vernier scale.Results Com-parison of TTF of the same type of file.① WKS:the TTF of files with the same tip diameter in a 30° curved root canal was longer than 60°(P＜0.05);The TTF of 25# nickel titanium files in the same angle curved root canal was longer than that of 20# nickel titanium files(P＜0.05).②PTG:the 20# nickel titanium files had a TTF longer than 60° in a 30° curved root canal(P＜0.05),while the 25# nickel titanium files had no statistically significant difference in TTF be-tween the 30° curved root canal and 60° curved root canal(P＞0.05);In a 30° curved root canal,the TTF of 20# nickel titanium files was longer than that of 25# nickel titanium files(P＜0.05).In a 60° curved root canal,there were no sta-tistically significant difference between the TTF of 20# nickel titanium files and 25# nickel titanium files(P＞0.05).③HCM:the TTF of files with the same tip diameter in a 30° curved root canal was longer than 60°(P＜0.05);The TTF of 20# nickel titanium files in the same angle curved root canal is longer than that of 25# nickel titanium filea.Compari-son of TTF of different files:in a 30° curved root canal,there was no statistically significant difference in TTF among the three types of 20# nickel titanium files(P＞0.05).The TTF of 25# WKS was longer than that of other files(P＜0.05);In a 60 ° curved root canal,the TTF of 20# HCM was longer than other files with the same tip diameter(P＜0.05),and the TTF of 25# WKS was longer than HCM with the same tip diameter(P＜0.05).The FL of 20# PTG,25#PTG,and 20# HCM in the 30° curved root canal model is significantly longer than that of 60°(P＜0.05),while there is no statistical difference in FL among 20# WKS,25# WKS,and 25# HCM in the 30° and 60° curved root canal models.Conclusion The anti cyclic fatigue performance of WKS is significantly superior to PTG and HCM in a 30° curved root canal.In a 60° curved root canal,20# HCM had a significant advantage in terms of anti cyclic fatigue performance compared to other files,while only 25# WKS had a significant advantage in anti cyclic fatigue performance compared to HCM.