Beijing's angry reaction came following a media report that Japan may reduce the selling price of Shinmaywa US-2 for India.
"I have noted this report. We hold no objection to the normal state to state cooperation including defence cooperation," Chinese Foreign Ministry spokesperson Hua Chunying told reporters here.
"But if the report is true that if someone is making an unrighteous move then this is very disgraceful," she added.
Hua, however, clarified Beijing had no problem as long as the cooperation, including of defence, was normal.
"But as reported that the Japanese government is to cut the price to sell weapons to India with an aim to pressurise China on the South China Sea issue and such attempt is targeted at China. If such a report is true then we don't think the purpose of such cooperation is righteous," she said.
China is growing wary of deepening ties between India and Japan, both of whom have asked it to respect the international court ruling on the South China Sea dispute.
The International Court of Arbitration in The Hague ruled in July in favour of the Philippines and rejected historical claims in the South China Sea by Beijing, which rejected the decision and branded it as "null and void".