Thirty people were wounded in the incident.
A section of the Meizhou-Dabu Expressway collapsed on Wednesday at 2:10 a.m. local time, triggered by heavy rain.
The 17.9-meter-long (58.7-foot) stretch of collapsed road caused 23 vehicles to plummet down the steep slope below, according to the Meizhou city government.
"As of 5:30 a.m. on (Thursday)... 36 people have died, and 30 people have been injured," the state Xinhua news agency said, adding that the injuries were not life-threatening.
Rain hinders rescue
President Xi Jinping called on officials to "go all-out in on-site rescue work and treatment of the injured, and arrange for the management of risks and hidden dangers in a timely manner", state broadcaster CCTV reported on Thursday.
The search operation has been complicated by steady rain, gravel and soil coming down at the accident site, putting rescue workers at risl, a fire department official told Chinese media.
CCTV footage showed excavators digging through the muddy hillside below the collapsed road as a crane lifted burnt and wrecked vehicles onto a lorry, reports DW.
CCTV reported that around 500 people have been deployed to support the rescue efforts.
The provincial government has "mobilized elite specialized forces and gone all out to carry out... search and rescue", Xinhua reported.
The southern province of Guangdong has witnessed a series of disasters due to extreme weather conditions in recent weeks.