Mobile　steel　building　is　a　prefabricated　building　built　in　a　factory,　with　advantages　on　moving　conveniently,　simple　structure　and　scalability.　There　are　still　not　enough　relevant　standards　and　requirements　to　conduct　the　design　and　construction　of　this　kind　of　buildings.　In　order　to　precede　to　theoretical　study　on　integral　structures　of　mobile　steel　buildings　a　method　which　used　to　set　up　finite　element　analysis　model　about　this　kind　of　structure　was　proposed.　This　method　is　based　on　finite　element　analysis　software,　ANSYS.　Using　this　method　a　two-story　structure　model　with　one　box　unit　in　each　story　was　analyzed.　Lateral　deformations　under　design　load　of　the　integral　structure　were　solved　out　by　these　finite　element　models　and　were　compared　with　the　former　experimental　results,　and　the　results　were　discussed.