Hi Meiying,
Check this out:
l_column = l_table->if_salv_wd_column_settings~get_column( 'YOURCOLUMN' ).
data textview type ref to cl_salv_wd_uie_text_view.
create object textview.
textview->set_text_fieldname( 'YOURCOLUMN' ).
textview->set_wrapping( abap_true ).
l_column->set_cell_editor( textview ).
Search the scn for: "ALV cell wrapping", "ALV cell wrap", "Wrap text in ALV", etc...
I haven't had the chance to test it, but I found a lot of information about this.
Regards,
Thales Schmidt