The annual summit between officials from the European Union and China has got off to a shaky start following criticism of China's closed economy.
Mr Barroso said there is a danger of Europeans seeing China as a threat
EU Trade Commissioner Peter Mandelson also said the Chinese government did not adequately protect the intellectual property rights of European companies.
But there were some warm words about the record levels of trade between the EU and China.
The summit is later expected to focus on the weakness of the Chinese yuan.
"Rebalancing the trade relationship is not a question of reducing Chinese exports to Europe," Mr Mandelson said.
"It is a question of improving the terms on which European companies trade here, about levelling the playing field and combating discrimination against foreign companies in the working of the economy," he added.
Trade between the EU and China is expected to top 300bn euros ($444bn; £215bn) this year but the EU's trade deficit with China is expected to rise to 170bn euros.
The weakness of the Chinese currency is a regular complaint from the EU because it makes it harder for domestic manufacturers to compete with their Chinese counterparts.
The yuan has been allowed to strengthen by 9.7% against the US dollar since its July 2005 revaluation, but it has weakened by about 11% against the euro.
"The considerable and growing trade deficit is adding to EU citizens' anxiety about globalisation, and is growing in political importance," EU Commission President Jose Manuel Barroso said.
"Indeed, there is a risk that the economic emergence of China is seen by Europeans as a threat."