The food scare caused a 6% fall in the China sales of KFC's parent Yum! Brands in the fourth quarter last year, deeper than its previous estimate of a 4% decline.
KFC will stop using chicken farms that have potential risk, improve the screening process of suppliers and step up self-inspections to address food safety concerns, the company said.
"It will always be our top priority to provide customers with the safest chicken with the best quality," Yum China's chairman and chief executive, Sam Su, said.
"We have seen some safety problems from the incident... and we aim to address the issue within the shortest time."
KFC also pledged to enhance communication with the government and the public, after the Chinese arm of Yum admitted last month that it failed to inform authorities about tests showing high levels of antibiotics in chicken.
Yum was aware of the issue through testing by a third-party in 2010 and 2011 but did not report to the authorities, the Shanghai government said in December.
China has seen several food safety incidents in recent years, including one of the biggest in 2008, when the industrial chemical melamine was found in dairy products which killed at least six babies and made 300,000 ill.