Trump accused Beijing of "massive theft of intellectual property" and of levying "unfair taxes on our companies," as well as "not helping with the menace of North Korea like they should."
"Other than that, they have been wonderful, right?" Trump asked rhetorically, to laughter from the Des Moines crowd.
Trump also brought Iowa Gov. Terry Branstad onstage and praised his pick to be the next ambassador to China, saying Branstad "knew how to get things done" and would improve "one of the most important relationships we have."
Trump cited Branstad's friendship with Chinese President Xi Jinping and vowed there would be "mutual respect" between Washington and Beijing.
"We're going to have mutual respect, and China is going to benefit and we're going to benefit," Trump said. "And Terry is going to lead the way."
Earlier Thursday, Trump flew to Columbus, Ohio to meet with several victims of the Nov. 28 terror attack at Ohio State University. Investigators say student Abdul Ali Razak Artan, 18, first rammed a campus crowd with his car before getting out with a knife and stabbing students before being fatally shot by police.
The president-elect spent about 30 minutes with some of the victims and their families.
"These are great people, amazing people," said Trump, who also paid tribute to the first responders who tended to the victims and shot the attacker. "The families have come through this so well."
Trump met with the families privately and aides did not immediately provide an accounting of what was discussed. But, in his brief statement to reporters, he took on the role of comforter-in-chief, avoiding the inflammatory rhetoric that has marked his response to other attacks.
Immediately following the Ohio incident, Trump had tweeted that Artan, a legal Somali immigrant, should not have been in the country. And last week, in nearby Cincinnati, Trump said lax immigration policies enacted by "stupid politicians" led to the "violent atrocity."
Later in Iow, he did not mention the attacker but declared: "This horrific assault is just one more tragic reminder that immigration security is national security. A Trump administration will always put the safety and security of American people first."
Trump also paid tribute to former astronaunt and U.S. Senator John Glenn, who passed away Thursday at the age of 95.
The president-elect called Glenn "one of our great heroes ... a giant among men, and a true American legend who inspired generations of explorers and dreamers. We will honor his legacy by continuing to push new frontiers in science, technology, and space."
On Friday, the president-elect is to make an appearance in Louisiana to boost the Republican Senate candidate ahead of that state's runoff before holding a rally in Michigan
The Associated Press contributed to this report.