The grocery sector in China was worth £607bn ($972bn) by the end of the 2011, showed research published by IGD.
The US market was valued at £527 for the same period, which means it ranks second.
By 2015, the research forecasts that the Brics countries (Brazil, Russia, China and India) will be the top grocery markets.
“China’s grocery growth story is phenomenal. Between 2006 and 2015, the Chinese grocery market is forecast to triple in value and to be worth nearly a trillion pounds,” said Joanne Denney-Finch, chief executive of IGD.
IGD forecasts that by 2015, the Chinese market will be worth £918bn compared to a US value of £675bn.
“This rapid expansion has been fuelled by three main factors: rapid economic growth, population and rising food inflation,” Ms Denney-Finch added.
The company said that many of the world’s largest grocery retailers would be looking to China, and not just at the major cities but also at second and third tier cities.
IGD said companies will also be looking to the Brics nations as the size of their markets grows.
“Many UK food and grocery companies are already pursuing this opportunity,” Ms Denney-Finch said.