In an interview with Reuters, Trump and his economic adviser Gary Cohn said China had forced US companies to transfer their intellectual property to China as a cost of doing business there.
The United States has started a trade investigation into the issue, and Cohn said the United States Trade Representative would be making recommendations about it soon.
"We have a very big intellectual property potential fine going, which is going to come out soon," Trump said in the interview.
While Trump did not specify what he meant by a "fine" against China, the 1974 trade law that authorised an investigation into China's alleged theft of US intellectual property allows him to impose retaliatory tariffs on Chinese goods or other trade sanctions until China changes its policies.
Trump said the damages could be high, without elaborating on how the numbers were reached or how the costs would be imposed.
"We're talking about big damages. We're talking about numbers that you haven't even thought about," Trump said.
US businesses say they lose hundreds of billions of dollars in technology and millions of jobs to Chinese firms which have stolen ideas and software or forced them to turn over intellectual property as part of the price of doing business in China.
Trump said he would be announcing some kind of action against China over trade and said he would discuss the issue during his State of the Union address to the US Congress on January 30.
In Beijing, foreign ministry spokesman Lu Kang said there were no laws in China to force foreign investors to transfer technology, but acknowledged such things may happen as part of "market behaviour" between companies working with each other.
"There is absolutely no government meddling in these actions," Lu told a daily news briefing on Thursday.
