Abstract: The PROTOS70 cigarette making machine was liable to produce cigarettes with defects,such as varied circumference or poor roundness of cigarette rod,tape impression on cigarette surface.By analyzing the working principle of rod forming section and causes of defects,the rod forming passage in garniture was prolonged and the structure of heater was improved.After that,cigarette circumference reached technical stan-dards,the tape impression on cigarette surface disappeared,and cigarette roundness was improved obviously.