he 5356 aluminum alloy rapid prototyping test was carried out by MIG welding. The morphology and microstructure characteristics of 5356 aluminum alloy moldings,effect of welding current and interlayer cooling time on molding structure and mechanical properties were observed by universal testing machine,optical microscope and scanning electron microscope,et al. The results show that there are mainly α（Al）,β（Mg,5,Al,8,） and（FeMn）Al,6, in the forming parts. The tensile strength of the forming parts increases with the increase of welding current in same interlayer cooling time. The highest tensile strength of the forming parts reaches 273.57 MPa when the interlayer cooling time is 60 s,the welding current is 90 A. The tensile strength get decrease when continue to increase the welding current. The tensile strength of the molded parts increases with the increase of interlayer cooling time in same welding current. When the interlayer cooling time is 60 s,the shape of the forming parts is relatively beautiful.