The unidentified man was stopped by two police officers when he approached the consulate early Sunday.
When questioned, he suddenly threw a glass bottle toward the consulate gate and burst into flames, said an Osaka (search) prefectural (state) police spokesman on condition of anonymity.
The policemen extinguished the fire, which was believed to have been fueled by some kind of flammable liquid, he said.
The man suffered burns on his left hand and across his body and was taken by ambulance to a nearby hospital, the spokesman said.
China has lodged a protest to the Japanese government over rising incidents of harassment directed at Chinese interests here amid escalating tensions between the two countries.
Postal packages containing razor blades, empty pistol shells and white powder have been sent to Chinese diplomatic missions across the country, according to police and media reports.
Vandals also smeared red paint on the Chinese ambassador's residence in Tokyo last week.
The incidents are believed to be in retaliation for massive anti-Japanese protests across China this month that have damaged Japanese diplomatic buildings, vandalized businesses and reportedly injured as many as four Japanese.
The tensions have been fueled by anger over Japan's wartime aggression and anxieties about Tokyo's military and diplomatic ambitions.