Thanks Rosenfeld again!
I read the link you gave carefully and check my Registry entries of ProfileList and made trials of adding/deleting users.
So i find the SID i posted is a local user and it's an orphaned sid.But I don't think it's a leftover which be used to install OS because of i'm sure it does not exist before. I figured out there was an user got access rights of the fold (i set the access of this fold strictly,only one person be permissible to read it)and the user was deleted by someone afterwards. So it is an attacker id if I am certain of my memory.
Now can i find out more specific of this SID on my machine, How?
By the way ,i find a ProfileList entry in Registry for a deleted user will be reserved when delete user with Computer Management Console, and when we delete user with 'User Accounts' the entry of profilelist will be deleted too.