I can't search the items through Barcode but all other fields are working well. An other problem I am encountering is "Can't call method "subfield" on an undefined value at /usr/share/koha/intranet/cgi-bin/cataloguing/additem.pl line 703." Please any one may guide me how can I fix it.
This sounds like a configuration issue rather than a bug in Koha code. I recommend you take your question to the Koha mailing list (http://lists.katipo.co.nz/mailman/listinfo/koha) where it will reach a wider audience.