Amway China will send its elite sales staff to the resort in multiple waves of 500 people, in five-day visits spread over four months, in autumn 2018 - a visit thought to be worth more than $50 million.
The deal was secured after a pitch by Tourism New Zealand, Destination Queenstown, the Queenstown Lakes District Council, Air New Zealand and Immigration New Zealand.
"This is by far the biggest incentive business New Zealand has ever won, and it sends a strong message that New Zealand is a serious contender in the global incentive market,'' Mr Key said in a statement.
China is New Zealand's second-largest and fastest-growing tourism market, boosting the country's economy by almost $1.7 billion last year.
The same statement quoted Queenstown Lakes Mayor Vanessa van Uden saying the local community would be excited to learn Queenstown was Amway China's chosen destination.
"Other communities right across the district will see these visitors, and feel the impact of their time here.
"We are developing strong links with China through our sister city and commercial relationships with Hangzhou. Amway's visit to Queenstown will provide the opportunity for our local business community to give them a unique experience that they will love,'' she said.
Destination Queenstown chief executive Graham Budd said it was a significant piece of incentive business and the town looked forward to delivering a world-class experience.
"This business will deliver a significant boost to our business community.''
Tourism New Zealand chief executive Kevin Bowler said the visit was timed for the off-peak season.
It would spread visitors across the season, supporting employment and bringing significant economic benefit, he said.
"The $50 million in value is estimated just from Amway's spend on the incentive alone. Each of the 10,000 staff will also contribute additional personal spend[ing]''
Mr Bowler said Immigration New Zealand played a pivotal role, as bringing such a large group into the country would require significant co-ordination and efficient visa processing.