Determine Whether a Given Column Name Is an Identity or Not

Select ColumnProperty(Object_id('Table_Name'), 'FieldName', 'IsIdentity')

Declare @colName varchar(100)
Declare @RetColName varchar(100)

Set @colName = 'FieldName' 

--Status column = 128 means its an identity column
Select @RetColName=[name] from syscolumns where status=128 and id=(select id
from sysobjects where name='Table_Name')

If @colName = @RetColName
   Print 'Its Identity'
Else
   Print 'Not an identity column'