Not really, people will just sell them.  If you really wanna give it to people that can use it.  Fold them, put them in a bag and put them beside your garbage , not in.   Within minutes some  super poor old lady, perhaps your underpaid cleaners. Will find them. And most certianly take them home for her family.  Too be nice, you might wanna put any old canned goods you dont plan on using in the bag too. 

Thrift collects old clothing, sells the ones they like and the rest is given to charity.
There are collection boxes in some Beijing venues. Not sure where...try The Local in Sanlitun area.
At some H&M stores you can find collection boxes. You get a discount when you donate clothes. I don't know where those clothes go to. Maybe to the kids who make their products...