The festival, which takes place in south eastern China, sees around 10,000 animals killed every year.
“I can barely bring myself to talk about the horrific Yulin Dog and Car Meat festival because it makes me sick,” he raged on Twitter.
“But unless we all do something about this, it won’t stop. We have to act now to stop these barbaric & disgusting events FOREVER [sic].”
The X Factor judge then urged people to sign Humane Society International’s petition to end the horrific event, which has so far gained almost 500,000 signatures.
It was reported this week that the animals are tortured to death, allegedly being torched before thrown in boiling water.
Simon, 55, is rarely apart from his two Yorkshire terriers Squiddly and Diddly, and he regularly addresses animal rights issues.
In September last year Simon donated £25,000 to the Manchester Dog’s Home, after an arson attack took the lives of 60 canines.
He was so moved by the efforts of two people who risked their lives to rescue the pups that he reportedly sent them on an all-inclusive holiday.
Sign HSI’s petition here and stop the Yulin Dog and Cat Meat festival.