The U.S. Senate voted 82-13 to confirm Branstad Monday afternoon.
Joni Ernst, Iowa's other U.S. Senator, said Branstad will be an "effective advocate" for U.S. interests in China.
The two first met as part of a sister-state exchange in 1985 when the governor welcomed a young agricultural official with a prestigious family background to Iowa to interact with local officials and live out on the farm.
Branstad will formally resign as governor on Wednesday, and immediately be sworn-in as U.S. Ambassador to China.
Shortly after, Reynolds will be sworn in as governor for the remainder of his term in a ceremony at the Capitol in Des Moines.
The 70-year-old is the longest serving governor in the U.S.at more than 22 years. Ben Cardin of Maryland, the top Democrat on the Foreign Relations Committee, declared Branstad "fully qualified" for the job. Branstad has also traveled to China several times on trade missions.
"Governor Branstad's confirmation today ends a career as Governor in which he attacked Iowa's workers and public schools, left the state budget in shambles, and on a couple of times occasion was rebuked by the Iowa Supreme Court for abusing his authority", the group's executive director, Matt Sinovic, said in an email.
An inaugural celebration for Iowa's first female governor, Kim Reynolds, will be hosted by the Republican Party of Iowa on June 2.
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If I would have got into the back of her and run into her fuel cell or something like that, it could have been a lot worse than it was.
Terry Davis, chairman of the Des Moines County Republicans, gave Branstad a B-plus grade as governor. He has been at the helm of Iowa government for more than 22 years.
After the Senate vote, Branstad thanked Trump and Vice President Pence for the nomination and the Senate for the confidence they have placed in him.
"She's kind of been the lead person on that, but I've been helping", Branstad said of the packing process.
I have no doubt he will stand strong for our American values, such as freedom of the press and religious liberty, and work to strengthen peace, stability and prosperity between our two nations.
Although his heart will always be in Iowa, I know that Governor Branstad will throw himself into this job whole-heartedly.
I'm pleased that he's now been called to serve as Ambassador to China.
That's expected to happen within the next few days.