Key said the agreement "will make doing business with China easier by reducing the costs of converting between the two currencies, and will stimulate trade and investment".
"Direct trading will also increase the integration between the New Zealand and Chinese financial systems, and deepen the economic relationship between the two countries."
The New Zealand dollar is only the sixth currency to be directly traded with the renminbi or yuan. The other currencies are the US dollar, Japanese yen, Russian rouble the Malaysian ringgit and the Australian dollar which gained that ability last year.
The Government would continue to work with New Zealand banks, other financial institutions, and exporters and importers who trade with China, "to raise awareness of the benefits of pricing in the two currencies and how direct trading can help".
In a related move, Westpac last night confirmed it had received approval from the People's Bank of China to act as a "market maker" or intermediary for direct trading of the New Zealand dollar and renminbi on the China Foreign Exchange Trading System.
The market maker licence allowed direct interbank trading of the New Zealand dollar and Chinese yuan, "meaning reduced transactional costs and over time increased liquidity to currency deals between New Zealand and Chinese trading partners" Westpac NZ chief executive Peter Clare said.
"Today's announcement helps make trade with China more efficient and will open future opportunities to strengthen the ties between the two countries"
Westpac general manager of corporate and institutional banking Karen Silk said Westpac was one of only two Australian/New Zealand banks to offer direct convertibility for mainland China transactions. The Herald understands the other bank is the ANZ.
Currency facts
# The New Zealand dollar has become only the sixth currency to be directly traded with the renminbi or yuan and only the 4th currency to be granted 'market maker' status allowing trade on China's forex system.
# Direct convertibility between the NZ dollar and renminbi cuts out the requirement and additional cost of converting via the US dollar for exporters and importers
# Westpac says the New Zealand dollar's new status should increase the visibility of this country's business in China.
# The renminbi (CNY) is now ranked as the 2nd most used currency in trade finance.