I have many many inscriptions of bad account publicity like it on my forum :
I have already deleted 500 members, but they are still in incription all the time :/
How can i block them please ?
What you are experiencing is Registration Spam and has nothing to do with WPForo, it could happen with any forum software.
You need to use anti-spam plugins with your WordPress installation and also activate WPForo anti spam features.
For plugins I recommend WPBruiser and Akismet.