A State Department official told CNN that Rank's resignation was a "personal decision", but several u.s. media quoted sources late Monday that pointed to the USA exit from the Paris Climate Agreement as the real cause.
The move has seen China emerge as the global champion in the fight against global warming, but some believe it may prompt Beijing to be more cautious towards Washington.
Before that, he had been a political counselor at the U.S. Embassy in Kabul, director of the State Department's Office of Afghanistan Affairs.
Acting US ambassador to China David Rank has resigned in protest against President Donald Trump's withdrawal of the US from the Paris climate accord. Branstad has been confirmed for his post but is undergoing ambassador training.
"We appreciate his years of dedicated service to the State Department", US embassy spokeswoman Mary Beth Polley said.
Contacted by Reuters for comment, Rank, a career foreign service officer who took over the post of deputy chief of mission in Beijing in January 2016, referred all questions to the us embassy. He couldn't back Trump on climate.
His resignation was first reported by John Pomfret, editor-at-large at SupChina.
As President Donald Trump strains alliances and relationships around the world, some of the nation's top career diplomats are breaking publicly with him, in what amounts to a quiet revolt by a cadre of public servants known for their professional discretion.
President Xi Jinping had urged Donald Trump to keep the United States in the Paris accord, but said that his country and France must "protect" the deal.
A day earlier, the acting ambassador to Britain, Lewis A. Lukens, tweeted his support of London's mayor, Sadiq Khan, in the wake of a deadly terrorist attack there.
The state department said the embassy's economics councillor Jonathan Fritz would be filling in behind Mr Rank immediately.
Smith, who continues to serve in Qatar, could not be reached for comment. "In all his years working for me, I never even knew his politics; exactly what you'd hope for from a career Foreign Service officer".
"Dave Rank is the best America has to offer", Scott Mulhauser, the former chief of staff at the U.S. Embassy in Beijing, told NBC News.