New Zealand Prime Minister Chris Hipkins leaves Wellington for Beijing on Sunday after securing the diplomatic coup of an invitation from China's leadership.
It's an honour Sir John received seven times as prime minister from 2008 to 2016.
"When you go to China as a New Zealand prime minister, you always get a very, very special experience," he told AAP.
"They turn out the bells and whistles.
"It's military parades, all that ceremony, and in the size and scale of such a massive emerging country."
Mr Hipkins will meet with China's President Xi Jinping on Tuesday but it is not yet clear whether he will walk away with an expanded trade deal or other agreement.
"From Chris Hipkins' point of view and from New Zealand's point of view, the trip is less about getting further concessions when it comes to the trade deal and more about just trying to firm up the relationship," Sir John said.
"The relationship is not nearly as firm footing as it was under my government."
NZ is often viewed as one of the most pro-China countries among Western nations and Sir John as its most pro-China leader.
Wellington secured a free trade deal in the months before his National government came to power, after which its worth grew exponentially.
Sir John maintains business interests in China and will travel there another three times this year, meeting with vice president Han Zheng.
He said Beijing became distanced from many in the West during the Covid-19 pandemic and Donald Trump's presidency, which demonised China.
Mr Hipkins raised eyebrows on Friday when he disagreed with US President Joe Biden's description of China's President Xi as a dictator.
Sir John doesn't attempt an answer when asked for his assessment.
Speaking at the National conference on Saturday, Opposition Leader Chris Luxon also demurred.
"I support the prime minister," he said.
Sir John said a level of closeness to Beijing should not mask who New Zealand's true allies were.
"That's without doubt our other Five Eyes partners starting with Australia and the United States," he said.
"That doesn't mean that we can't have a very successful and prosperous relationship with China based much more on trade.
"That gives us a level of influence in a positive way in China, that those who choose to throw stones ultimately don't have."
He said NZ could disagree firmly and politely on issues such as China's treatment of Uighurs and eroding human rights in Hong Kong.
Sir John said Mr Hipkins would benefit from the trip less than four months from the October 14 election.
"He's had such a terrible run domestically in the last few weeks, with three ministers having to resign on his watch," he said.
"Success is probably just being out of the country.
"He'll want to come away with a narrative that says he's established his own relationship with China but he hasn't traded away any of the values and principles that he thinks his Western allies would want him to communicate."
