Exports rose 15.3 percent in the month compared to May 2011, The New York Times reported Monday.
The surge pushed May past December 2011 as the biggest ever month for Chinese exports, which grew in March, April and May.
Compared with a year earlier, May exports to the United States jumped 23 percent while exports to the European Union in the same period rose only 3.2 percent.
However, despite labor costs in China rising at a double-digit pace, Chinese imports dropped in prices in April, the Times said.
Prices are falling because many Chinese firms are investing in labor-saving machinery. In addition, inflation slowed in China this year with producer prices in May off 1.7 percent from May 2011.
Effectively, deflation among Chinese producers and inflation in the United States have given the exchange rate a 2 percent boost in China's favor this year.