They were seen off at the Phnom Penh International Airport by Senate President Chea Sim, National Assembly President Heng Samrin, Prime Minister Hun Sen, other government officials, royal family members and Chinese Ambassador to Cambodia Zhang Jinfeng.
During the stay in China, Sihanouk, his wife and Sihamoni are scheduled to attend the opening ceremony of the Beijing Olympics on August 8.
Sihamoni will return home in about two weeks, a royal palace official said at the airport, adding that Sihanouk and his wife will stay much longer.
The couple’s last trip to China for medical checkup was in April 2008.
The 85-year-old former king suffers from diabetes and has had colon cancer. He abdicated his throne to Sihamoni in October 2004.
Editor: Wang Hongjiang