Hi Duong. Marketing and exporting are two completely different activities/disciplines. While you can market your exporting business, exporting generally requires a product or service of some sort. Whereas marketing is how you let others know what product or service you have to offer.
I hope that this helps.
LaRue gave you a good answer to your question. One thing to keep in mind if you are in the export business, are the different laws and taxes that exist in other countries which you have to abide by. Also, your country probably has laws that govern and control any such types of business exchanges which you must be aware of.