Another South Korean identified by his surname Chang was executed on Thursday in Qingdao, Shandong Province on drugs charges.
His death follows the execution a day earlier of two other South Koreans on similar charges.
A Foreign Ministry official here said Chinese judicial authorities notified Seoul of his execution at 4 p.m. on Thursday.
Chang (55) was arrested in 2009 for smuggling 11.5 kg of methamphetamines from North Korea to China, where he sold them.
He was sentenced to death by a court in Qingdao in May 2012 and appealed to a high court in Shandong Province. But his sentence was upheld by the high court in June 2013 and later in December by the Supreme People's Court.
Chang is the fifth South Korean to be executed in China since the two countries established diplomatic relations in 1992.
Beijing notified the South Korean Consulate General in Qingdao of Chang's arrest three days after he was nabbed, according to the ministry. A South Korean consul interviewed him and helped his family visit him in prison.
Beijing informed Seoul of the Chinese court's decision to execute him in May this year, some five months after the decision was made.
The ministry official said the delay was not unusual. "It normally takes five or six months for China to formally notify another country of such a court decision given internal procedure."
Foreign Minister Yun Byung-se and Ambassador to China Kwon Young-se asked Beijing to grant Chang a stay of execution for humanitarian reasons, saying he has a family in South Korea.
But the Shandong high court wrote to the Consulate General in Qingdao on Aug. 1 saying that Chang will be executed as early as this week.
China has particularly harsh penalties for drug-related offenders, Chinese or foreigners, perhaps due to painful memories of the Opium Wars of the 19th century.
In 2010, a Japanese man was executed for possession of 1.25 kg of methamphetamines, so it was unlikely that Chang would avoid execution after he was nabbed with 11.5 kg.