The world's largest retailer will reimburse customers who bought the "Five Spice Donkey Meat" 50 yuan (USD 8.25), a spokeswoman told AFP.
The company would also independently DNA test all of its "high risk" meats in China, a procedure which is not required by retailers under Chinese food laws, the spokeswoman said.
Wal-Mart would also cooperate with food officials in the eastern province of Shandong with their probe into the "adulteration incident", said a statement posted on Sina Weibo, a Chinese Twitter equivalent.
The Shandong Food and Drug Administration had previously said the "Five Spice Donkey Meat" product contained fox.
"We are deeply sorry for this whole affair," said Wal-Mart's China president and CEO Greg Foran according to the Weibo statement, posted yesterday.
It did not give an explanation for how the contamination happened, but Foran added that the company would increase its focus on "supplier management".
Donkey meat is not a Chinese staple meat dish, but is commonly consumed as a snack.
China has seen several food safety scares in recent years, including one in which the industrial chemical melamine was added to milk formula in 2008, killing at least six babies and making 300,000 ill.
Wal-Mart plans to open up to 110 new stores in China over the next two years, according to the company's website.