Hi
please advise me according to asme standard about welding slag removing inspection standard
thanks

Your question is not clear. There is not such a standard. You mean slag removing before welding on? Please read UW-32 here below:

UW-32(a) The surfaces to be welded shall be clean and
free of scale, rust, oil, grease, slag, detrimental oxides, and
other deleterious foreign material. The method and extent
of cleaning should be determined based on the material to
be welded and the contaminants to be removed. When
weld metal is to be deposited over a previously welded
surface, all slag shall be removed by a roughing tool, chisel,
chipping hammer, or other suitable means so as to prevent
inclusion of impurities in the weld metal.

Regards.
Mauro

Dear Mehrdad,
I agrree with previous answer you know it is mandatory to clean surface of the weld from slag and other contamination and you can follow mentioned code(UW-32(a)).
Best Regards,
Khodabandeh