No.
GOG has 3 refund options.
Option 1: Game In Development. 14 Days money back, no questions asked.
Option 2: Wrong purchase. Bought a game, didn't download it, wish to return it. 30 days from date of purchase (I think), refund only if nothing has been downloaded.
Option 3: Game doesn't work on supported systems. Support tries to help, but is unable to. Refund applied.

You do not qualify for any of the 3 options, so a refund is not possible. GOG is willing to refund you with Wallet Funds, but cannot return "real money".

Thanks for the reply.I'm wondering why they say my pc doesn't meet the system requirements?I mean the game is released in 1999.

What Windows are you using?

From Swat 3's GOG System Req Page :

Works on: Windows (XP, Vista, 7)

If you have WIndows 8 or 10, then you probably will not get a refund.

I believe JMich is right about refunds, but the first prize would be to fix the problem with the game in the first place. I peeked in the SWAT forum and saw somebody post a link to http://www.swat3lastresort.info/index.php/fix-framerate-problems which has some suggestions that seem worth trying.

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Newer hardware can break older software, unfortunately. From now on, always check the "Works on" tab (to see if your version of windows is supported and the system requirements (and exceptions) below "Works on" to be eligible for a refund.

The image below shows what I mean.

you can also create a simple windows xp virtual machine with virtualbox.
Since this game is old, and it is compatible with windows xp you should be able to run it in a modern computer in a virtual machine.

That probably won't run properly because virtual machines can't run 3D acceleration of the Glide variety too well.

I'm new on GOG(SWAT4 rerelease brought me here),I don't know much GOG. Thank you all for the clarification and solution:)

Just about every piece of software has at least a few basic requirements to be met, without which it will not run (or at least, the developer/distributor can't guarantee they'll run; in this case, GOG's requirements probably represent the lowest specs they tested the game on). For SWAT 3, GOG's min reqs are as follows (taken from the store page): I would guess that the problem in your case is that you're on Win 10 or 8? They apparently couldn't get this title running satisfactorily or reliably on those operating systems, and therefore don't support its use on them. They were, however, nice enough to offer you a discount anyway, so be glad for the store credit. :)

Of course, as Barefoot_Monkey noted above, just because the game doesn't work very well "out of the box" doesn't necessarily mean there's no way to fix things. Besides checking the GOG subforum for that series for fixes or workarounds, maybe check out [url=http://pcgamingwiki.com/wiki/SWAT_3:_Tactical_Game_of_the_Year_Edition]the entry on PCGamingWiki[/url]. EDIT: Assuming you keep the game, that is.

In addition to all the advice above, you might also consider taking the wallet funds and using them to spend on another game. GOG has a huge library, so there is a good chance you'll find something you like.

Yeah,I'll take that offer. Thank you! :)

My virtual machine can run 3D acceleration... sure I use vmware but I think virtualbox can support some 3d acceleration:
http://i.imgur.com/nDKcNMG.png
(it's in italian but you can see that there is directx 10 and opengl 3.3 support... since swat 3 is not a new game this is enough)