Hi I created a db then add many tables , insert into them a lot of rows , it reached 70MB
then i deleted all the tables
but when i shrink my db , it did not shrink! it stay 70MB
Sounds like there are transactions (probably the DELETE's!!) which are still in the transaction log. Run a transaction log backups, and then try the shrink again. If that doesn't work you probably have a "stuck" transaction - stop/starting SQL Server will usually clear that (by forcing a checkpoint on the DB), but if not please come back and ask again.
No one has followed this question yet.