The zookeepers made the cake out of ice, bamboo, fruit and other treats, KNSD-TV, San Diego, reported.
The cake took an entire month to create and was 5-feet tall, zoo officials said.
When Bai Yun saw the cake Saturday, she walked over and began licking the ice and eating the bamboo, KNSD-TV said.
She shared the treat with her cubs.
Bai Yun was born at the Wolong Giant Panda Research Center in China, and moved to the San Diego Zoo in 1996.
She has given birth to six cubs at the zoo, KNSD-TV said.