Friction stir welding (FSW) is a new solid-state plastically joining process developed in the beginning of the 1990’s. The influence of the stirrer’s shape and process parameter on joint quality was studied. The investigation result shows that the microstructure and mechanical property of the joint welded with truncated cone and screw welding pin is better than the joint welded with cylindrical welding pin. When welded with proper stirrer and parameter, maximum joint tensile strength can reach 98% of the parent material. And microhardness of friction stir welded MB3 was considered with the grain size distribution in the weld zone.