BEIJING—China plans to clamp tighter controls on Chinese companies seeking to invest overseas, intensifying efforts to slow a surge in capital fleeing offshore amid tepid growth and an uncertain economic outlook.

The State Council, China’s cabinet, will soon announce new measures that subject many overseas deals to reviews of “strict control,” according to people with direct knowledge of the matter and documents reviewed by The Wall Street Journal.

Targeted for particular scrutiny by the pending measure are “extra-large” foreign acquisitions valued at $10 billion or more per deal, property investments by state-owned firms above $1 billion and investments of $1 billion or more by any Chinese company in an overseas entity unrelated to the investor’s core business.

While the government has been plugging holes to keep more money at home in recent months, the new measures are the first to go after big deals by China Inc.

In doing so, the controls underscore Beijing concerns about capital flight and a weakening currency. They also come amid an overseas buying binge by Chinese companies. Total overseas direct investment rose more than 50% to $145.9 billion in the first nine months of this year from the same time a year earlier, according to official data.