6005A-T6 Al-alloy profiles were subjected to friction stir welding (FSW) at a high welding speed of 1000 mm/min, while the effect of mechanical grinding of the butt face on the microstructure and mechanical properties of the butt joints was investigated. The results show that the microstructure of “S” line is more obvious in the FSW joint with unpolished surface, compared to that of the traditional FSW joint with polished surface. Both FSW joints exhibited similar microhardness distribution and tensile properties, and all the samples failed at the lowest hardness zones, i.e., the heat affected zone (HAZ), during tensile tests. The fatigue properties are almost the same for both FSW joints with unpolished and polished surfaces, while the fatigue strength was 105 MPa and 110 MPa, respectively. At high stress amplitudes the samples fractured at the base material, but the sample failed at the HAZ at a low stress amplitude of 120 MPa, and two crack initiation zones were found. All of the fracture surfaces exhibited typical three zones, namely crack source zone, propagation zone and final fracture zone. The results indicate that the static tensile and dynamic fatigue properties of FSW joints were not affected by the surface mechanical polishing.