The country's foreign exchange reserves, the world's largest, reached $1.68 trillion by the end of March, an increase of $153.9 billion from the end of last year, the central bank said on Friday.
The year-on-year increase was nearly 40 percent, according to a statement from the People's Bank of China.
The spike in reserves has aroused concerns that "hot money", or speculative capital, is flowing into the country on a large scale.
"While growth of the trade surplus is on the decline, the reserves are increasing rapidly, which means much of the capital comes from the capital account," Zhao Xijun, a finance professor of Renmin University of China, said.
"Compared with the current account, it is harder to monitor capital coming via the capital account," Zhao said.
Meanwhile, the growth of China's broad measure of money supply, or M2, which includes cash and all types of deposits, slowed to an annual 16.3 percent in March from 17.5 percent in February, the central bank said.