China on Monday lowered its figure for economic growth for last year to 7.7 percent from 7.8 percent, the National Bureau of Statistics said, in an unexpected downgrade for the key number.
The world's second-largest economy has long been looked to as a potential driver of global recovery, but has put in a mixed performance in recent months.
The new figure posted on the National Bureau of Statistics website remains the lowest for gross domestic product growth since 1999, when it expanded 7.6 percent.
China's GDP stood at 51.9 trillion yuan ($8.5 trillion) for 2012, the NBS added.
The country officially overtook Japan as the world's second-largest economy in 2010 and the growth figure is a key statistic for global investors, businesses and institutions.
Like other economies, China regularly revises its annual GDP figures although it usually does so in an upward direction.
But now its leaders are looking to steer it towards a hoped-for soft landing after years of high-speed expansion.
The statistics bureau cited "more comprehensive and reliable fundamental" information for the change.
The revision was "preliminary", it added, and the figure could be altered again as more data was obtained.
The 7.7 percent result remains above the government's economic growth target for last year of 7.5 percent.
Beijing normally announces a conservative growth target and generally exceeds it.
The target for this year is also 7.5 percent. But after an acceleration to 7.9 percent in the final three months of 2012, growth slowed to 7.7 percent in the January-March period and 7.5 percent in the second quarter.
Growth in the first six months of the year came in at 7.6 percent, the NBS said in July, calling the performance "generally stable" and within expectations.
Despite two straight quarters of slowing growth, recent data for the current third quarter have been surprisingly solid so far, causing some economists to believe that it may be poised to stem the slide.
The 2012 figure compares with expansions of 9.3 percent in 2011 and 10.4 percent in 2010 and underscores a slowing trend after years of double-digit growth.
China's leaders say they want to retool the country's economic model away from a reliance on big ticket government-led investments and make private spending the key driver for what they hope will be expansions that are sustainable.
President Xi Jinping said in April that China's days of "ultra-high speed" growth are probably over, but he said the country can "sustain a relatively high speed of economic growth".
The reliability of China's statistics often prove vexing for economists who follow the country.
Even new premier Li Keqiang has expressed doubts, telling the US ambassador to China in 2007 when he was a top provincial official that some Chinese data were "man-made" and thus unreliable, according to leaked US diplomatic cables.
Li said he focused on only three figures -- electricity consumption, rail cargo volume, and the amount of loans issued -- when evaluating the provincial economy, according to a confidential memo released by the WikiLeaks website in late 2010.
"All other figures, especially GDP statistics, are 'for reference only,' he said smiling," according to the cable.