He was addressing the National Party's South Island conference in Wanaka yesterday.
Mr Key said although Australia was New Zealand's biggest market, China was the fastest growing.
"The other interesting thing, let's say by next year there's about half a million Chinese tourists coming to New Zealand and about one and a-half million Aussies, those 500,000 Chinese will spend more each year than all the Aussies combined.''
In addition, he said, Chinese spending in New Zealand would produce about $1billion in GST.
The total tourism spend in New Zealand this year, including both overseas visitors and internal travel, was $32.6billion, Mr Key said.
He was speaking to about 180 National Party supporters at the Wanaka conference.
Referring to his ejection from Parliament on Wednesday last week, Mr Key said he was planning to be a "very good boy from now on'' and expected "wing man'' Gerry Brownlee to "dive tackle'' him next time Speaker of the House David Carter rose to his feet.
