Trade surplus stood at 239.6 billion yuan (about 33.79 billion US dollars) last month, expanding 41.8 percent from one year earlier, according to data released by the General Administration of Customs (GAC).
The drop comes after a surprise 3.3% rebound in July despite the yearlong battle with Washington and weakening global demand.
China's global exports declined by three per cent in August.
Sluggish domestic demand was likely the main factor in the fall, along with softening global commodity prices. In recent months, China's exports to the United States, Europe, South Korea, Australia and Southeast Asia have declined.
China and the US will hold face-to-face trade negotiations in Washington in the coming weeks, after a rapid deterioration in relations last month left global investors reeling amid increasing evidence the conflict is harming both nations.
Exports fell to just over $214 billion, while imports fell 5.6 per cent to just under $180 billion, figures from the Beijing statistics office showed.
Facing downward pressure and headwinds from trade frictions, China vowed to take further steps to ensure the stability of employment, the financial sector, foreign trade, foreign investment, domestic investment and expectations, according to a statement released after a State Council executive meeting Wednesday. Analysts had forecast a surplus of $43-B for August.
China hit back with levies of its own, and let its yuan currency fall to offset some of the tariff pressures.
Appearing on CNBC, Kudlow said President Donald Trump believes the Chinese want to make a deal and that talks are continuing.
But there was no indication that any planned tariffs on Chinese goods would be halted, and markets expect a lasting peace between the two countries to be more elusive than ever.
In April 2019, the United States said it wanted to put tariffs on $11.2 billion worth of goods from the EU.
Many analysts expect export growth to slow further in coming months, with more U.S. tariff measures due to take effect on 1 October and 15 December.
China reported a trade surplus of $34.84-B last month, compared with a $45.06-B surplus in July.
The two sides have agreed to hold further discussions in Washington in early October, later than expected.
"The global economy is approaching the turning point of a recession, and external demand will, for sure, become worse and worse", Morgan Stanley Huaxin Securities' Mr Zhang said.