"The Chinese people have lost a good and true comrade," Mr Jinping said in a message read at the beginning of the nightly news on the country's main TV channel.
"Comrade Castro will live forever."
Mr Castro was "a great man of our time," said the President.
"History and people will remember him," he added.
Mr Jinping said that relations between the two communist nations grew quickly thanks to Mr Castro's efforts after diplomatic ties were established in 1960.
Even though the two countries shared an ideology they remained distant due to Cuba's closeness to the Soviet Union, China's rival from the 1960s, until Mao Zedong's death in 1976.
There was a rapprochement after the fall of the Soviet Union, with Chinese leaders visiting Cuba several times.
President Jinping "visited his old friend Fidel Castro" in July 2014, CCTV said.
Fidel Castro visited Beijing in 1995.