The main ports in the world's third-largest economy processed an estimated 9.2 million containers in April, the official Xinhua news agency said, citing transportation ministry figures.
Overall cargo traffic last month was down 1.9 percent from a year earlier to 500 million tonnes, Xinhua said.
China's exports fell 17.1 percent in March, their fifth straight monthly decline, according to the latest government figures.
However, recent data indicates that manufacturing activity expanded in April after months of contraction.
China's economy grew 6.1 percent in the first quarter, the lowest level in at least a decade.