do you notice the little stores nearby the high-school or elementry school? most of them sell note books, pensels, toys and wrapping paper to children. find these places and take a look , i am sure you will find what you looking for.

Another option is to go to what i've dubbed 'toys paradise' behind Hongqiao Pearl Market (west gate of Tian Tan). You can find wrapping papers in all shape, colours and material... and it's super cheap too. Head for the 2nd floor and you'll find all you need...

Umm...hello never tried Walmart yet? Also, during christmas some places may do free gift wrapping for you. There is a little store across from the Walmart around the CBD area that sells wrapping. 

Good news bad news thing.

Good news is that you can buy it almost everywhere.

Bad news is that it only comes in red.

I posted this a year ago but am once again struggling to find decent Christmas wrapping paper in Beijing. April Gourmet only has really tacky paper which I wouldn't consider wrapping my presents in.