Shi Baikui, 27, from the eastern province of Shandong, was arrested last May at an Internet cafe in the Chinese capital more than 48 hours after committing the theft.
"Shi was given a 13-year sentence in prison, fined 13,000 yuan ($2,000) and deprived of his political rights for three years" at a court in Beijing, his lawyer Huang Changyong told AFP.
According to the state-run news agency Xinhua, Shi broke into the heavily guarded former home of Chinese emperors in May last year where he stole nine valuable items including gold and jewels.
Police managed to recover six of the stolen items but three pieces worth an estimated 150,000 yuan remain missing, Xinhua said.
News reports at the time said the stolen items -- valued at up to 10 million yuan -- dated from the early 20th century and included jewellery boxes and women's make-up cases.
Shi's theft is the fifth on record at the Forbidden City. The last person was sentenced to life in prison after trying to rob the ancient imperial palace in 1987, according to state media.
The Forbidden City, one of Beijing's most popular tourist attractions, was first built in the early 15th century and served as the imperial palace of China's Ming and Qing Dynasties.
It provided the setting for the 1987 Oscar-winning film "The Last Emperor", the first feature film to be granted permission by the Chinese government to be shot at the exclusive location.