Wang Baoan made the comments at a briefing held one week after the bureau released economic growth data for the fourth quarter and 2015.
He reiterated that China's GDP data was reliable.
China's annual economic growth slowed to 6.8 percent in the fourth quarter, the weakest since the financial crisis, adding pressure on a government that is struggling to restore investor confidence.
The government reported annual economic growth of 6.9 percent in 2015 - the poorest showing in 25 years and slowing from 7.3 percent in 2014.