China and New Zealand agreed to expand their burgeoning trade relationship during a state visit by President Xi Jinping Thursday, including a deal to allow television co-productions to be aired on Chinese media.

Wellington became the first developed nation to sign a free trade agreement with Beijing in 2008, and Xi joined New Zealand Prime Minister John Key in hailing the success of the agreement.

"The New Zealand-China relationship shows that countries with different political systems, history and cultural traditions and at different stages of development can constructively cooperate together," they said in a joint statement.

Xi's visit, off the back of his trip to Brisbane for last weekend's G20 summit and a state visit to Australia, focused on broadening the 2008 agreement in key areas, including encouraging television co-productions between the two countries.

"(It) will allow programmes co-produced by New Zealand and Chinese companies to be officially broadcast on Chinese TV, where potential viewing audiences are huge," Key said.

They also signed off on a food traceability scheme in the wake of an infant formula contamination scare last year which resulted in New Zealand milk powder being pulled from Chinese shelves until it was revealed as a false alarm.

Dairy remains New Zealand's largest export to China, with consumers keen on the country's "clean, green" image.

China displaced Australia as New Zealand's largest export market last year, and two-way trade between the nations was almost NZ$22 billion ($17.4 billion) in the year to June 2014, according to official figures.

Xi received a 21-gun salute and a traditional Maori welcome in Wellington before meeting Key, who presented him with an All Blacks rugby union jersey bearing the lucky number 8.

Meanwhile, Xi's wife Peng Liyaun celebrated her 52nd birthday by receiving an honorary doctorate from Wellington's Massey University in acknowledgement of her career as a singer.

"This is the best gift for me for my birthday," she said through a translator.

About a dozen protesters were outside the Xi-Key meeting but they were outnumbered by more than 100 pro-China students waving flags and banners.

Xi will travel to Fiji on Friday to meet leaders from Pacific island nations, where China has become a major aid donor in recent years.