China is the world's fastest-growing energy market. U.S. government data show it overtook the United States in September as the biggest oil importer, driven by rising auto ownership and strong economic growth.
The communist government is eager to obtain Russian supplies, which would help to curb China's reliance on crude from the unstable Persian Gulf, which Beijing sees as a potential security weakness.
Russian energy companies operate two pipelines to move oil to China and one to deliver gas but further development has been slow.
China imported 170 million barrels of oil from Russia in 2012, according to Xinhua.
The Tianjin refinery will have an annual capacity of 110 million barrels, Medvedev said, according to Xinhua. It will be built by state-owned China National Petroleum Corp., which will own 49 percent, and Rosneft, which will own 51 percent.
In June, the two companies signed an agreement for Russia to supply 2.5 billion barrels of oil valued at an estimated $270 billion to China over the next 25 years.