If you know why you got banned why don't you remove it and apply for re-inclusion?

Thanks,
I sent reinclusion form in sitemap and it backs after a week.

Google also ban for using duplicate content, Keyword stuffing and hidden text etc. It might be a possibility I doubt.

Google will not ban for duplicate content.

Check this; :rolleyes: The shortest distance between your site and your SEO is a straight line.
http://www.seroundtable.com/archives/003398.html

There's a big difference between being banned and being devalued. Since duplicate content can be an accident you won't be banned for it. But it can cause you to rank poorly. That way intentional duplicate content is ineffective and accidental doesn't cause a site to be banned permanently when it really isn't justified.

when i checked your site, there was spammy page title Vietnam Travel,Vietnam Hotel,Vietnam Tour,Vietnam Holiday,Vietnam Vacation,Vietnam Travel Agent,Vietnam Tour Operator,Vietnam Tourism,Vietnam Tourist Guide. Better you make it as naturally as possible.