Objective: To evaluate the clinical effect of the ProTaper nickel-titanium rotary instruments in preparation of curved root canals. Methods: Sixty-five teeth with curved root canals were treated with ProTaper instruments using crown-down technique and obturated with lateral condensation method. The efficiency of preparation and obturation was analyzed by radiographs before, during and after the operation. Results: No blockage, ledge, zip and apical transportation were found in all cases. The instruments could keep the curvature and flow of curved canals. The operative time was short, and endodontic flare-up seldom occurred. Two files were fractured during instrumentation. Conclusion: The ProTaper NiTi rotary instruments can prepare curved root canals effectively and quickly. Meanwhile, the problem of instrument fracture should be prevented.