Guo departed San Francisco for Shanghai on October 18 in a bid to break the non-stop solo trans-Pacific record.
Footage released by the US Coast Guard showed Guo's 97-foot trimaran Qingdao China drifting across the waves hundreds of kilometres west of Hawaii, its red sail emblazoned "Peace and Sport".
Conditions were calm, and the vessel's automatic identification system was still transmitting, but no-one was visible on board.
Both a US Navy helicopter crew and a Coast Guard Hercules overflying the vessel had been unable to contact Guo, it said.
Guo, 51, is the first Chinese sailor to complete a non-stop solo circumnavigation of the globe and is by far the country's biggest sailing star.
A former scientist, he departed San Francisco for Shanghai on October 18 in a bid to break the non-stop solo trans-Pacific record.
The US Coast Guard said it was called Tuesday when Guo's team had not received notification from him for 24 hours.
The sailor had previously been "in constant contact" with the Maritime Rescue Coordination Centre China and his family and was "not likely to miss scheduled calls", it added.
A post on a verified Weibo social media account for Guo's team said they had observed his speed slowed on Tuesday and attempted to contact him, but he did not answer either satellite calls or internet communication.
The US searchers had found a broken sail in the water, they added.
A US Navy spokeswoman told AFP that an amphibious navy ship, the USS Makin Island, had been diverted to investigate the vessel and deploy a smaller boat to directly board the Qingdao China to look for Guo.
Online Chinese responses were concerned but hopeful on Thursday.
"Oh Captain, please return home safely!" said one poster.
"Praying and praying, you must return home safely," said another.