have you tried using vertex groups or weight painting to assign each bracer to its respective bone?

Joining them into one model is what you want, but you'll still need to assign each individual bracer to a separate bone (or bones).

trgdy has the right idea. You can test this more simply by following these steps:
http://i.imgur.com/EwMb03I.jpg

Thanks for replying, my vertex group list is empty
http://imgur.com/sZhfYGC
The vertex groups, must I create it on my own or is it already available ?
edit : I have assigned each bracer to the respective bone, but my only problem is i want to export both bracer as 1 file instead of 2

I think you got the first part working, but just in case you need an explanation: you need to parent the object to the bone rig before anything shows up in that list.

As for exporting as one model, you will need to combine both meshes into one object. Do this before assigning bones to anything (I think you can do it afterwards, but it's better practice to assign bones to everything once the model is more or less complete).

You can join objects by select both objects from object-mode and then pressing "ctrl+j" to join them. Now the model should be one object. Go into edit mode and rig the model as before. Then export the model when done.

I think I get it, but I did parent the bracer but still nothing shows up at Vertex Group
It supposed like this right ?
http://imgur.com/9nmbDnr
http://imgur.com/x3IMskk
edit : I noticed something at Slardar's original bracer, they apply Armature modifer and tick the Vertex Groups, I tried the modifier on my meshes but it didn't show up

Not sure how this is so difficult, but you need to do exactly what I said: FIRST join the two meshes into one object (you didn't do that according to your picture). SECOND select the combined model, then shift+select the bone rig and press "ctrl+p" > "with empty groups" to parent the model to the rig. Then follow the steps in this picture: http://i.imgur.com/EwMb03I.jpg

Just tried it, it worked !
And, I'm the one that wrong, I never tried Ctrl+P. Before starting this discussion, I directly parent the object using Object Tab.
Forgive me for fussing over this simple matter.
Again, thank you so much

Please expect to see my new set soon. Criticize it as well

I'm glad it worked.