The controversial internet personality is currently fighting extradition to the US, where the authorities want him to stand trial for copyright infringement and racketeering charges.
Megaupload was shut down when Dotcom was arrested at his New Zealand home earlier this year, but the site's co-founder insists that there are measures in place to ensure that its successor does not go the same way.
Dotcom wrote on Twitter: "Quick update on the new Mega: Code 90% done. Servers on the way. Lawyers, Partners and Investors ready. Be patient. It's coming".
When asked by a follower whether he is concerned that the US authorities will clamp down on his new venture, he responded: "That will be IMPOSSIBLE. Trust me."
The Megaupload founder is also working on a music service called Megabox, which will enable artists to sell their work directly to customers while generating revenue from advertisements.
Meanwhile, Dotcom's extradition trial is scheduled to take place next March, after being postponed from August this year.