In this paper, friction stir welding process parameters (material position, rotation rate, traverse speed, tool offset) were prepared to study theirs influences on microstructure, mechanical properties and residual stresses of friction stir welded joints of 5083 Al alloy to AM60B cast Mg alloy. Sound friction stir welded joints were obtained with intermediate rotation rate of tool (1000 rpm) and proper traverse speed (50-150 mm/min) when 5083 Al alloy was on advancing side, no tool offset, and the highest tensile strength (170 MPa) of the joints could reach up to 75% of that of the AM60B cast Mg alloy base material. The intermetallic compounds (IMCs) consisted of Al3Mg2 and Mg17Al12 were observed in the severe intercalated zone. Fracture which was featured by the cleavage feature always occurred near the joint interface because of the brittle IMCs, which indicated the typical brittle fracture. The residual stresses across the welds were distributed asymmetrically and tensile residual stresses on the advancing side were higher than that on the retreating side due to the higher heat input on the advancing side.