I solved with this code:

<form string="XXXX" version="7.0">
  <sheet>
    <script>
      $(document).ready(function(){
        $('.ui-dialog').css({'width': '1000px', 'left':'166px'});
        $('.oe_form_sheet_width').css({'MAXwidth': '1000px'});
      }); 
    </script>
    <field name="name" />
  </sheet>
 </form>