His plane is due to use Chinese airspace and traditionally the Holy Father will send greeting to the leaders of all countries he flies over.
In 1989 China refused to let St John Paul II fly through the country when he was visiting South Korea.
Relationships between Beijing and the Holy See have been bad more than 60 years since the Communist Party came to power.
But in recent years the Church has started more dialogue with the country including a letter written by Pope Franics soon after his election.
The Pontiff wrote to the Chinese President and it's thought he replied.
Vatican spokesman Fr. Federico Lombardi, said it was unclear what Francis' greetings might involve.
The Pope will visit Seoul on August 13.