That follows an 12.3 percent year-on-year drop in July and a 11.1 percent rise in June.
The company said in a statement that the decline in August was due to sluggish sales of light commercial vehicles.
The company's sales in the first eight months of the year came to about 785,400 vehicles, up 9.4 percent from the same period a year earlier.
Nissan, which operates a car venture in China with Dongfeng Motor Group Co Ltd, aims to sell 1.4 million cars in the country this year, up 10.6 percent from a year earlier.
Nissan's Senior Vice President Jun Seki said in May that the company aims to achieve annual China sales of 2 million cars by 2017-2018 as it bolsters its business in the world's largest car market.