China is the most irreligious country in the world.One of the reasons for irreligion in China is its history with religion. Two events in the 1800's are indirectly responsible for this. The Taiping Civil War(1850-64) and Boxer Rebellion(1899-1901) destroyed Chinese people's faith in religion as these movements were basically mass cleansings of specific religions.
These were followed by the rise of Communism after WW2 and the disastrous Cultural Revolution in 1966, at the end of which the concept of religion was removed from the Communist Party. Article 36 of the Chinese Constitution nominally protects the rights of religious freedom and as of today, however, only 5% of Chinese people believe they are religious.