Hello 'cememe...',
The following link explains what to do when there is a problem. As you are new to ebay it contains some of the most important information you will need:
http://pages.ebay.ca/help/buy/item-not-received.html
When you return an item you must do so with a tracked (Delivery Confirmed) service. Have a look at what it costs to mail a package like that to China from Canada:
https://www.canadapost.ca/cpotools/apps/far/business/findARate?execution=e1s1
You do not state the reason for the return. This matters because it makes a difference as to who must pay return shipping.
If you simply don't like the jacket or you think it is a cheap quality, you must pay return shipping.
If you ordered a red one and you received a blue one, or you ordered a size L and received size XS, that is a seller mistake and the seller must pay return shipping.
Usually the first thing to do when you are unhappy with a purchase is contact the seller. Have you tried that?
If you can post more info about the item and return, other members here can help walk you through the process.