A helical ribbon impeller without a shaft is considered to be effective not only to reduce the stagnant region around the shalt but also actually to prevent polymer growing at the surface of the shaft. Chemical process industries demand truly effective mixing impellers which overcome conventional impellers such as those with a shaft that have problems in actual operation. In this study, a new type of helical ribbon impeller, which consists of frame and blades. is supported by computational fluid dynamics studies, which are useful to analyze the effects of ribbon and frame dimensions on Row and mixing characteristics. Also the difference between the conventional ribbon impeller and the new type impeller are examined. The results of the computations show that the flow pattern of the new impeller largely depends on the ribbon and frame dimensions, and that a set of optimum dimensions can minimize the mixing time. In particular, the frame not only contributes a mechanical strength but also changes the mixing pattern formed by the ribbon blades to effectively shorten the mixing time. The computational results also show that the new impeller has a flow pattern quite different from that produced by the conventional ribbon, and that the new impeller＇s mixing time is reduced to approximately a half of the conventional ribbon＇s.