I try to use Mikrotik as hotspot gateway. I have the question format that mikrotik send to radius for password.

When debugging the the freeradius, I can see the request for password is like

User-Password = '~\025\014Α\002\236\256\272F/\273b\351\014('

what format is that? when I use radtest, the radius receive normal plain text.

User-Password = 'MAC'

Problem is radius is rejecting the request, even the password is correct.

Have you checked that the shared secret is right?
This happens generally when shared secret is not same on both ends(NAS and radius server)