Sir Keir is seeking to strengthen trading and cultural ties between the two nations after years of acrimony.
But he has faced criticism from opponents at home over the risk posed by China to the UK’s national security and Xi Jinping’s human rights record.
The PM – who will meet President Xi on Thursday – said the trip will bring benefits to the UK and it was important to maintain a “strategic and consistent relationship” with the world’s second largest economy.
As he arrived at the airport in Beijing, Sir Keir was greeted by a delegation of Chinese government officials and presented with a bouquet of flowers. Union flags were seen flying in Beijing’s Tiananmen Square.
Addressing the 60 British business leaders accompanying him on the trip, the PM said: “On this delegation, you’re making history. You’re part of the change that we’re bringing about.
“We are resolute about being outward-looking, about taking opportunities, about building relationships…and always being absolutely focused on our national interest.”
For a UK prime minister, the politics of engaging with China is tricky.
China has been accused of committing crimes against humanity against the Uyghur population and other mostly-Muslim ethnic groups in the north-western region of Xinjiang.
There has also been criticism over the treatment of Jimmy Lai – the Hong Kong pro-democracy media tycoon – who is facing a life sentence in prison.
In addition to China’s human rights record, there are concerns about the scale of its espionage activities in the UK, with the head of MI5 recently warning that Chinese state operatives presented a daily national security threat.
Sir Keir declined to be drawn on what he would seek to raise with Chinese leaders.
“In the past, on all the trips I’ve done, I’ve always raised issues that need to be raised, but I don’t want to get ahead of myself on the specifics until I’ve had the opportunity,” he told reporters travelling with him.
He added: “Part of the reason for engaging with China is so that issues where we disagree can be discussed, and the issues where we agree can be progressed, and so that’s the approach.”
