The National Bureau of Statistics said the increase provided further evidence of the country's economy strengthening.
The August year-on-year increase compared with an increase of 11.6 percent in July.
The data measure profits of companies with annual revenues of more than 20 million yuan ($3.26 million). The survey included 41 industries.
In the first eight months of this year, the firms' total profits rose 12.8 percent to 3.5 trillion yuan ($571.8 billion), the Xinhua News Agency reported.
The report said electricity, heat production and the supply industry had their profits jump 70.1 percent in the first eight months while makers of computers, telecommunication and electronics had theirs rise 29.2 percent.