Tian, speaking at the first news conference since the meetings opened last Friday, said the Great Barrier Reef proposal was based on data from Australia and recommendations from an advisory body.
Australian Environment Minister Susan Ley, who is in Europe lobbying Unesco delegates against supporting the in-danger listing, was not immediately available to comment.
Her office on Monday released a report by the Government-funded Australian Institute of Marine Science that indicated widespread recovery of the reef's coral. Monitoring by the institute found coral cover had increased during the respite from severe weather over the last year.
"The release of the full report underlines our view that the World Heritage Committee proposed listing had not been based on the latest information," Ley said in a statement.
Australia reacted angrily when the draft was released last month.
"This decision was flawed. Clearly there were politics behind it," Ley said, without mentioning China by name.
Relations between the two nations have soured in recent years, with Australia blocking Chinese technology and investment in key infrastructure, and China using tariffs and other measures to reduce its imports from Australia.
Australia was warned in 2014 that an in-danger listing was being considered for the Great Barrier Reef, which was designated a world heritage site in 1981.
The draft decision said that Australia's long-term plan for the reef, a network of 2500 reefs covering 348,000 square kilometres, "requires stronger and clearer commitments, in particular towards urgently countering the effects of climate change".
"We acknowledge very much the work which has been done in Australia, but our text in the draft decision ... is a proposal for putting the site on the list of world heritage in danger because of the threats which were identified," said Mechtild Roessler, the Unesco director of the World Heritage Committee.
Ernesto Ottone Ramírez, the assistant director-general for culture at Unesco, said that an in-danger listing should be viewed as a collective call for action from all the member states.
"It's something that should be seen as something positive and not, as what we heard from some of the authorities in other countries, as a punishment," he said, joining the news conference from Paris. "It's how we preserve our heritage for future generations."