Friction welding technique performs superior characteristics on mechanical properties and on production performances. However, the application of this technique is limited in joining of round bar materials due to the lack of positioning control capability. This limitation can be overcome by introducing recent servo system. This study is carried out to clarify the effects of process parameters on mechanical properties of positioning controlled joints of aluminum alloy. A6061 rods with square cross section. The positioning controlled joining was successfully performed. The mechanical properties of them are almost equivalent to the joints fabricated by conventional friction welding process, when sufficient upset distance is applied. Defects of imperfect joining are observed at the corner of the joints with square cross section, with the upset distance is insufficient. Higher upset load makes a better contact area at the weld interface resulting in narrower softened zone and larger upset distance eliminating weld imperfection.