Furthermore, many Chinese who do know the language don't speak it well, the official Xinhua News Agency reported Thursday.
An official campaign to promote Mandarin has been conducted the third week of September every year since 1998. Still, said ministry spokeswoman Xu Mei, about 30 percent of the population, or 400 million people, don't know how speak it.
Of the 70 percent who do speak "putonghua," as it is also known, a large number aren't fluent.
The Communist Party has promoted Mandarin for decades as a way of unifying the country, the BBC reported.
Chinese speak thousands of dialects, and a number of ethnic groups have their own languages.