The index has surged by just over 34 per cent since the start of 2019.
In Australia, the ASX200 broke through 7000 points for the first time, led by a boost in tech stocks.
America's Dow Jones, S&P500 and Nasdaq indices all rallied on the trade news.
"It's definitely good news because it's been such a point of tension over the past 12 months," Mark Lister, head of private wealth research at Craigs Investment Partners, said.
"The relationship between the US and China seems to be one of collaboration and trying to get some progress going - that's a big reason why sharemarkets are where they are at," he said.
"It means we can relax a little bit in terms of the trade tensions in the short term and re-focus on some of the other issues such as corporate earnings," he said.
The Financial Times said US President Donald Trump was likely to make the deal a centrepiece of his November re-election campaign.
But the paper said the limited concessions from Beijing and the damage inflicted to key sectors of the US economy during the course of the trade war, including manufacturing and agriculture, could prove a political liability come November.
The US has agreed to reduce tariffs on Chinese products, but is expected to keep tariffs on about US$380b in goods.
According to the Peterson Institute for International Economics, average US levies on Chinese imports will be 19.3 per cent even after the deal takes effect - more than six times higher than before the trade war began in 2018.
Financial markets have taken some comfort from the apparent willingness of both parties to paper over the cracks of their fractured trade relationship.
For New Zealand, what happens in the Chinese economy will be important, particularly if the economy continues to slow.
China is New Zealand's biggest trading partner. Australia is its second biggest, and Australia's biggest partner is also China.
Lister said New Zealand had "hitched its wagon" to the Chinese growth story - directly and indirectly - because of its trade with the PRC and Australia.
He said investors' focus was now likely to turn to the US corporate reporting season, which starts next week.
However, the US-China trade relationship is likely to remain a recurrent theme throughout 2020.
In the deal, China agreed to loosen some longstanding barriers to trade in food and agriculture — mostly related to health standards — that had applied to products including infant formula, poultry, beef, pork, rice and pet food.
It also makes it easier for US grain producers to obtain biotech-related approvals for genetically modified crops.
The relaxing of these barriers should make it easier for US farmers to export more goods to China — which is the subject of another chapter in the agreement.
In the agreement, the parties agree to recognise the importance of intellectual property protection.
"China recognises the importance of establishing and implementing a comprehensive legal system of intellectual property protection and enforcement as it transforms from a major intellectual property consumer to a major intellectual property producer," it says.
"China believes that enhancing intellectual property protection and enforcement is in the interest of building an innovative country, growing innovation-driven enterprises, and promoting high quality economic growth," the agreement says.
