The Global Times tabloid, which is published under the People's Daily newspaper, the mouthpiece of the Communist Party, conceded in an editorial that it was "understandable" for Japan to recall the bombing.
"But it must be pointed out that the ceremony directs people's attention only to the fact that Japan is a victim of atomic bombing, but turns a blind eye to the reason why," the English-language editorial said.
"Ceremonies like this water down the fact that Japan was also a perpetrator of war crimes. This shows how adept Japan is at scheming and calculating."
Another atomic bomb was dropped on the city of Nagasaki three days later, killing more than 70,000 people.
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Japan surrendered on August 15, 1945, though opinion remains divided on whether the unprecedented use of the weapons was justified.
Japan held its solemn annual commemoration today, at which Prime Minister Shinzo Abe vowed to push for global denuclearisation, saying Tokyo would submit a fresh resolution to abolish nuclear weapons at the UN general assembly later this year.
"Abe wants to normalise the status of his country, but without a full retrospection over Japan's war crimes," it said.
China, which often emphasises its own victimisation at the hands of foreign powers, is itself gearing up to commemorate Japan's World War II defeat, planning a massive military parade through central Beijing.
China says more than 20 million of its citizens died as a result of Japan's invasion, occupation and atrocities.