Fluent simulation software is used to establish a variety of typical large-format forming bin structures， and SpaceClaim software is used to extract the flow field of the established large-format forming bin， to obtain the fluid domain inside the laser-selective melting forming bin， and to conduct flow field characteristics for various structures. The positions above the forming table and below the lens are used to analyze the flow field characteristics and flow field uniformity of various structures.The research results show that a stable and uniform gas flow field is formed inside the porous wind wall forming bin.At 20 mm above the top of the forming table， the flow rate is in the range of 284~308 mm/s； At the position below the laser lens， the overall shielding gas rate is in the range of 142~175 mm/s； and a circulating gas flow from the inlet to the outlet can be formed inside， and the soot that is not discharged in time can be discharged out of the forming bin after multiple flows.