The American billionaire would put the money into the construction of an exclusive hotel and yacht club complex in the Black Sea resort city Yalta, said Evhen Chervonenko, Ukraine's minister of transport.
Trump, after August negotiations with the Ukrainian government, acquired rights to develop real estate under his name in Kiev and Yalta.
If the projects are financed completely, Trump's contribution will be $500m, Chervonenko said.
The investment would convert Yalta, currently a somewhat dilapidated resort favoured by citizens of the former Soviet Union unable to afford trips elswhere, into one of Europe's top summer destinations, he added.
It would also be by far the biggest foreign investment in Ukraine's hospitality industry, where non-Ukrainian businessmen have experienced difficulties with corrupt government officials and mobsters.
Besides ground-up construction of hotels, Yalta's entire waterfront would be overhauled and a world-class yacht club be installed, he said.
Most new building would take place at the Yalta freight port, whose current use by cargo ships undermines Crimea's summer tourism business.
The yacht club would replace the ship port, Chervonenko said.