Cao told Tongan journalists at a press conference in Nuku'alofa that trade relations were mutually beneficial.
This comes amid diplomatic tension after China reached a security pact with Solomon Islands.
Cao expressed his unease about negative news coverage of Sino-Tonga relations.
"There are some irresponsible words and irrational attitudes towards China Tonga friendly relations and cooperation. As journalist you may find that you are short of reliable and genuine sources of information because there is much fake news in media," he said.
